Fluid handling – Line condition change responsive valves – Safety cut-off requiring reset
Reexamination Certificate
1999-11-03
2001-01-16
Chambers, A. Michael (Department: 3753)
Fluid handling
Line condition change responsive valves
Safety cut-off requiring reset
C137S458000, C137S512300, C137S614200
Reexamination Certificate
active
06173734
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to flow control valves, and more particularly to leak arresting mechanical flow control valves that regulate fluid flow between a minimum flow rate and a maximum flow rate.
2. Description of Related Art
Valves used in the regulation of fluid flow are well known in the art. Valves can be used to maintain fluid flow in a particular direction, or as a safety feature to prevent too high of a flow rate or too low of a flow rate. Some valves are mechanical devices that use the pressure in a fluid flow to compress a spring or other resisting member, thereby allowing the fluid either to pass through the valve or be blocked by the valve.
The present invention is directed to a flow regulating (or safety) valve which allows a constant fluid flow in a predetermined range, as opposed to a pulse flow. Valves used for this purpose are too numerous to identify, but the present invention includes a new feature not found in the prior art valves, namely, a purely mechanical leak detecting function. That is, a mechanical valve which regulates the fluid flow to maintain a flow rate within a predetermined minimum and maximum flow rate, and further mechanically closes the valve when either a small or large downstream leak occurs. Thus, while prior art safety valves will close shut, and thereby stop the fluid flow if a major leak occurs due to the sudden increase in the fluid flow rate, the prior art valves lack the ability to close shut in the event of a small leak such as might occur due to a small breach in the downstream fluid line or the failure of a downstream component. This situation could be of critical importance if, say, the fluid is hazardous or flammable, if the fluid line is not regularly maintained due to its location or conditions of use, or if subsequent damage from such a line breach would be economically or environmentally unacceptable. The response of the valve may be the only indication that a small leak has occurred. The present invention solves the problem that the prior art valves fail to address.
OBJECTS AND SUMMARY OF THE INVENTION
The present invention is a reliable, mechanical valve which does not rely on any electronics or human interaction to perform its leak arresting function. The leak arresting valve includes a first stage which includes a spring loaded member for limiting the flow rate through the valve to a predetermined range, i.e., between a minimum flow rate and a maximum flow rate. Above a maximum flow rate, a flow arresting element such as a ball, gate, poppet, diaphragm, or other known valve blocking mechanism is driven by the force of the fluid flow resulting in a large pressure differential across the element, into a non-flow position causing fluid flow through the valve to cease. Below the maximum fluid flow rate, the position of the flow arresting element is such that fluid flows by, around, or across the element thereby permitting fluid to pass through the valve. In a second stage of the leak arresting valve, a second flow arresting element is biased in a closed position and requires a minimum flow condition to open the second stage. Below a minimum flow rate the fluid flow is insufficient to open the valve, thereby precluding flow through the valve. Additionally, the second stage is set up such that a locking mechanism will lock the second stage flow arresting element in a closed position upon the occurrence of a small downstream leak, but will open normally under normal operating conditions. The leak arresting function, i.e., the locking of the valve in the closed position, is achieved by the higher pressure upstream, actuating locking members which lock the second stage flow arresting element in the closed position.
Under normal start up condition, the difference in the upstream and downstream pressures with reference to the second stage flow arresting element is large. The second stage flow arresting element transitions due to the pressure difference in a rapid manner past the trigger for the locking mechanism before suitable time is given for the trigger to respond. Conversely, under the influence of a downstream leak, the back pressure on the valve is reduced, and a smaller pressure differential across the second stage flow arresting element is present. The pressure differential is ultimately used to actuate the locking mechanism that restricts the linear translation of the flow arresting element. This configuration will exist even after the differential pressure increases within the normal range. Only after the leak condition is corrected can the valve be reset and returned to a normal configuration. Once the upstream fluid flow is terminated, the pressure differential is eliminated through the valve and all leak conditions, whether small or large, can be reset and all locking members are retracted to their original positions. In this manner, the leak arresting valve resets automatically upon the equalization of the pressure, and mechanically detects the presence of a downstream leak.
REFERENCES:
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patent: 4976281 (1990-12-01), Berglund
patent: 5462081 (1995-10-01), Perusek et al.
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Chem Tec Equipment Company, Excess Flow Valves 3 pages.
Chem Tec Equipment Company, EFV HP Series Manual Reset, 3 pages.
Chem Tec Equipment Company, EFV MRS Series Manual Reset, 3 pages.
Chem Tec Equipment Company EFV Series Manual Reset, 2 pages.
Filterchem, Pressure Relief Valves, 2 pages.
Cunningham Patrick J.
Martis Mark C.
Olivas John D.
Brightvalve LLC
Chambers A. Michael
McShane Thomas L.
Price and Gess
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