Fluid handling – Line condition change responsive valves – Direct response valves
Reexamination Certificate
1999-10-19
2001-02-27
Rivell, John (Department: 3753)
Fluid handling
Line condition change responsive valves
Direct response valves
C137S515700
Reexamination Certificate
active
06192926
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a safety valve of the type used to regulate the pressure in fluid-transporting installations. More specifically, the invention relates to a safety valve for use in pneumatic circuits.
BACKGROUND OF THE INVENTION
Pressure control in a hydraulic circuit is carried out using valves. Known in this respect is the use of safety valves, or relief valves, in order to maintain a constant pressure in the hydraulic circuit and thereby prevent pressure peaks which could harm the various parts of said circuit. These pressure peaks, which can give rise to the phenomenon of water hammer, must therefore be controlled effectively.
Conventional safety valves, used mainly in hydraulic circuits, essentially comprise a body provided with an inlet and an outlet, a closing element or gate which is mounted hinged to the valve body and which divides the aforesaid inlet and outlet, a seat formed in said body and against which said gate rests, hinge means of the gate on the valve body, and means for keeping the gate in position against the seat. One of the main disadvantages presented by this type of valve, and more specifically the valves known as “clapet” valves, is that when a large volume of fluid has to be evacuated the means to keep the gate in position can generate considerable pressure variations which are a function of the movement of the gate, which in turn depends on the different quantities of fluid to be evacuated.
The disadvantages are considerably greater when this type of valve is used in pneumatic circuits. This is the case due to the fact that the effect of water hammer is more critical. The flow of air in a pneumatic circuit causes the gate to undergo an oscillatory movement which is harmful to it. Indeed, it has been found in practice that the gates of these valves fail by breakage of their hinge pin due to fatigue. Gate failure is extremely important from a technical point of view and from a financial point of view. In installations which work with a pneumatic circuit with large air flows, as, for example, the circuits for sewage water treatment plants or vacuum installations, operation of the installations must be stopped every 2 or 3 months in order to replace the valves. This has a negative effect on the cost of maintenance of the installation and means that a schedule of operation of the installation must be drawn up in function of the maintenance stops that have to be carried out ever so often.
It must further be taken into account that the problems deriving from failure of conventional safety valves can, for example, cause a pneumatic valve to turn in opposite direction due to overpressure in the system, thereby causing breakdown of that system.
The prior art comprises valves with a structural arrangement designed to reduce the cited oscillatory movement of the gate and, therefore, what is called the “flag effect”. Some solutions have been proposed in this respect in an attempt to reduce said effect, although such configurations result in a design that is too expensive for the installation.
OBJECTS AND SUMMARY OF THE INVENTION
The aim of the present invention is to provide a valve which can be fitted in a pneumatic circuit and which has structural characteristics capable of solving all the disadvantages presented by the valves included in the state of the art.
Another aim of the invention is to provide a valve that is very simple to manufacture, which comprises a small number of parts and whose functioning is effective under any working conditions.
The valve of this invention, which will be described below, achieves both aims, and has a cost significantly lower than the valves used for the same purpose under the prior art.
Along general lines, the valve of the invention is of the type described above, that is, one that basically comprises a body with an inlet and an outlet, a moving gate that separates said inlet and said outlet, a seat formed on said body and so designed that said gate rests against it, hinge means of the gate on the valve body and means for keeping the gate in position against the seat.
The special feature of the safety valve of the invention lies in the fact that said means for keeping the gate in position against the seat essentially comprise a body attached to one end of the gate, the gate and said body being hinged to the valve body in such a way that both can rotate around a single hinge pin. Said hinge pin is arranged eccentrically with respect to said body attached to the gate, in such a way that the gate is kept in equilibrium when the pressure inside the valve exceeds 0.1 bar.
The layout and structure of said means for keeping the gate in position against the seat allow the position of the centre of gravity of the gate with respect to its hinge pin to be altered. In this respect, the body which is attached to the gate and rotates together with it around a single hinge pin mounted eccentrically with respect to said body allows it to act as a counterweight to eliminate the “flag effect” of the valve gate, that is, its oscillatory movement. Breakages of the pin due to fatigue are thus reduced considerably, and as a result the servicing intervals for the installation and, in short, the useful life of the valve, are lengthened.
In accordance with the invention, the hinge pin is aligned with the point of contact between the gate and the seat of the valve body. The design of the valve thus conceived allows to guarantee the fluidtightness of the unit and, therefore, the regularity of the advance caused by the flow of the pump, thus assisting correct operation of the system. In this respect, sealing means are fitted between the gate and the seat of the valve, preferably consisting in an O-ring.
In order to facilitate maintenance operations, where such are required, the invention makes provision for the gate hinge pin to be detachable.
REFERENCES:
patent: 1018569 (1912-02-01), Kelty
patent: 2048088 (1936-07-01), Wagner
patent: 2637264 (1953-05-01), Harmon
patent: 3783893 (1974-01-01), Davison
patent: 4266569 (1981-05-01), Wilson
patent: 4353390 (1982-10-01), Karpenko
patent: 4473526 (1984-09-01), Buhler et al.
patent: 5031659 (1991-07-01), Gonzales et al.
patent: 5738087 (1998-04-01), King
patent: 5921862 (1999-07-01), Ucciardi
Rivell John
Steinberg & Raskin, P.C.
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