Fluid handling – Systems – Flow path with serial valves and/or closures
Utility Patent
2000-04-18
2001-01-02
Lee, Kevin (Department: 3753)
Fluid handling
Systems
Flow path with serial valves and/or closures
C137S614200, C141S021000
Utility Patent
active
06167908
ABSTRACT:
CROSS-REFERENCES TO RELATED APPLICATIONS
This application claims the priority of German Patent Application, Serial No. 199 17 431.8, filed Apr. 19, 1999, the subject matter of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a valve assembly for an apparatus under pressure, such as a vessel under pressure.
Pressure vessels, in particular gas bottles under high pressure, are used for receiving and delivery of various gases. The gases are contained in the pressure vessels either in a gaseous state under high pressure, or, for example in case of carbon dioxide, in liquid form under pressure. Other gases, e.g. acetylene, are contained under pressure in the vessel and dissolved in a carrier medium such as acetone to prevent a danger of explosion.
A typical construction of a conventional valve assembly includes a valve casing which has a connecting pipe for attachment to a pressure vessel, and a discharge pipe, with the connecting pipe and the discharge pipe being connected by a fluid-carrying pathway. Integrated in the valve casing are a shut-off valve for regulating a flow of fluid through the fluid pathway, and a control valve which includes a spring-loaded valve body having a fluid duct forming part of the fluid pathway. At its side proximate to the inlet pressure zone, the valve body includes a sealing element which is movable by the valve body against a valve seat for sealing the fluid pathway and thereby separate the inlet pressure zone from the outlet pressure zone.
Valve assemblies with pressure regulators are used for setting and/or regulating an outlet pressure with respect to the higher inlet pressure prevalent in the pressure vessel. A valve assembly of this type is disclosed, e.g., in the German Pat. No. DE 34 41 348 A1, and includes a pressure reducing valve, integrated in the valve casing, and a pressure regulating valve acted upon by a preset spring tension of a control spring. The pressure regulating valve reduces the static pressure on the outlet side (outlet pressure zone). As long as a pressure fluid is able to flow through the valve, the spring tension keeps the valve open and the valve body is lifted, i.e. away from the confronting valve seat. When the pressure builds up in the outlet pressure zone, the valve body is moved against the valve seat and the valve closes, as a consequence of the pressure buildup in conjunction with the effective surfaces of the valve body and the control spring. A modification of the preset spring tension allows an adjustment of the maximum pressure in the outlet pressure zone.
On many occasions, pressure vessels contain special gases, which, for safety concerns or due to their particular use, e.g., as clean gases in the technical industry, as medical gases or as immersion gases, should not be mixed with other gases or air. For that reason, pressure vessels are equipped with valve assemblies with integrated residual pressure valves. Such a valve assembly is described, e.g., in European Pat. No. EP 0 458 253 B1 or German Pat. No. 197 09 096 A1. The residual pressure valve is configured as a check valve which clears its valve seat and opens when the interior pressure exceeds the preset residual pressure. When the interior pressure drops below the preset residual pressure, a spring tension acts on the check valve to close the valve seat. Thus, the residual pressure valve prevents a complete pressure decrease in the pressure vessel when the discharge valve is open, as soon as the internal pressure of the gas drops below a preset minimum pressure. In this manner, there is no need to evacuate or flush the pressure vessel each time a new charge is introduced. Moreover, the residual pressure valve prevents ingress of foreign substances from outside.
Although conventional valve assemblies have shown their usefulness, they are still too bulky and complex in structure.
SUMMARY OF THE INVENTION
It is thus an object of the present invention to provide an improved valve assembly, obviating the afore-stated drawbacks.
In particular, it is an object of the present invention to provide an improved valve assembly with integrated residual gas pressure lock, which is compact and simple in structure while yet reliable in operation.
These objects, and others which will become apparent hereinafter, are attained in accordance with the present invention by providing a valve casing including a connecting pipe for attachment to an apparatus under pressure, and a discharge pipe, with the connecting pipe and the discharge pipe being connected by a fluid pathway; a shut-off valve for regulating a flow of fluid through the fluid pathway; and a control valve including a spring-loaded valve body which includes a fluid duct forming part of the fluid pathway, with the valve body having one end accommodating a first sealing element movable by the valve body against a valve seat for sealing the fluid pathway and thereby separate an inlet pressure zone from an outlet pressure zone, and another end accommodating a second sealing element movable by the valve body against a seal seat, wherein the second sealing element rests against the seal seat to block the fluid pathway in the outlet pressure zone, when a residual pressure in the apparatus under pressure drops below a predetermined level.
Thus, in accordance with the present invention, the valve body of the control valve has in addition to the sealing element in the inlet pressure zone, a further sealing element in the outlet pressure zone for bearing upon the confronting seal seat, when the residual pressure in the pressure vessel drops below a predetermined level.
The residual pressure can be defined by constructive means. It is dependent on the spring force of the control spring and its spring characteristic as well as on the distance between the valve body and the seal seat. It is however also possible to so configure the valve assembly that the residual pressure is adjustable.
In the valve assembly according to the present invention, the functions of the control valve and the residual pressure valve are combined in a united design, and assumed by a valve body. Response or closing of the residual pressure valve can be implemented according to the present invention by exploiting the deflection of the control spring that acts on the valve body. As soon as the inlet pressure drops below the outlet pressure, the control spring of the control valve relaxes and shifts the valve body in translational motion, with the second sealing element moving against the confronting seal seat to seal the inlet pressure zone against the atmosphere. Thus, a valve assembly with integrated pressure regulating valve in accordance with the present invention realizes a residual gas pressure lock in a simple manner, without need for additional components. The residual gas pressure lock prevents a full emptying of the pressure vessel via the discharge pipe, thereby ensuring that the pressure in the pressure vessel is always higher than the atmospheric pressure, and thereby prevent a gas exchange with the ambient atmosphere. Also, ingress of air humidity, leading to corrosions in the pressure vessel, are averted to ensure the purity of pressure fluid contained in the pressure vessel. Complex steps for evacuating the pressure vessel before recharging can now be omitted.
Other advantages of a valve assembly according to the present invention include the absence of additional bores for receiving a separate residual pressure valve, thus facilitating the manufacture, and the easier installation of the individual components as well as easier maintenance.
There are many ways of configuring the control spring, e.g. by various elastic elements, such as a pneumatic spring. Also the valve body may be configured in various manner, e.g. as piston or as membrane. According to one embodiment of the present invention, the valve body is configured as a stepped piston which is guided in a bore of the valve casing and acted upon by a helical compression spring. This configuration is reliable in operation, wi
Feiereisen Henry M.
Lee Kevin
VTI Ventil Technik GmbH
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