Fluid sprinkling – spraying – and diffusing – Processes
Reexamination Certificate
1999-11-18
2001-04-10
Scherbel, David A. (Department: 3752)
Fluid sprinkling, spraying, and diffusing
Processes
C239S542000, C239S533100, C239S547000
Reexamination Certificate
active
06213408
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates to fluid flow regulators and, in particular, it concerns flow regulators based on the principles of labyrinth flow-attenuation devices such as are used in irrigation applications.
Various types of flow attenuators and flow regulators are known for achieving slow release of a fluid from a relatively high pressure source, such as is required for drip irrigation emitters. The most common of these, referred to here as “labyrinth-type devices”, achieve flow attenuation by providing a circuitous flow path along which kinetic energy is dissipated through turbulence.
Labyrinth-type devices have been adopted widely in drip irrigation applications for a number of reasons. The use of turbulent flow for flow attenuation allows the size of the passageways to be relatively large, thereby facilitating passage of dirt without blocking the labyrinth. The turbulence itself helps to prevent accumulation of dirt. And the devices may be mass produced from plastic by injection molding at very low cost.
Nevertheless, while labyrinth-type devices offer effective flow attenuation, they fail to provide flow regulation. In other words, the rate of fluid output remains highly dependent upon the supply pressure to the device. This results in uneven irrigation with lower regions and regions closer to the fluid supply often receiving more irrigation than higher regions and regions further from the supply.
To address this problem, a number of pressure-responsive flow regulating devices have been developed. These devices generally employ an elastomeric diaphragm which is exposed on one side to the fluid supply pressure. The other side of the diaphragm faces an outlet chamber having a centrally disposed outlet and which is supplied through a pressure-reducing flow path, typically a small labyrinth. Any increase in the supply pressure flexes the diaphragm so as to reduce the size of the flow path through the outlet, thereby regulating the outlet flow rate.
Flow regulating devices of this type, referred to herein as “diaphragm-type regulators”, have been shown to provide substantially constant flow over a considerable range of supply pressures. The use of elastomeric diaphragms, however, is accompanied by various problems. Most notably, the elastomeric materials employed undergo relatively rapid aging such that their elasticity and other mechanical properties may vary significantly over a period of a year or even a few months. Since the low flow rates of drip irrigation require regulation of the outlet clearance on the scale of fractions of a millimeter, even small variations in the elastic properties of the diaphragm may cause pronounced changes in operation of the flow regulator. An additional shortcoming, even in new diaphragm-type regulators, results from the long response time (or “relaxation time”) of the elastomeric material, i.e., the time taken to return to its previous shape or to adopt its new shape when the pressure changes suddenly. This time lag may result in significant flow variations at times of sudden variations in supply pressure such as when the fluid supply is switched on or off.
An alternative approach to achieve regulated flow using a labyrinth-type flow attenuator is proposed by U.S. Pat. Nos. 5,400,973, 5,609,303 and 5,829,685 to Cohen. In these devices, an elastomeric membrane is used as a displaceable wall which lies across the top of a set of baffles. The wall is displaced by variations in supply pressure to successively contact more or fewer baffles, thereby varying the operative length of the resulting labyrinth. Here too, the devices suffer from the aforementioned limitations due to aging of the elastomeric materials, and due to the materials' long response times.
A further shortcoming of all devices currently in use which employ a labyrinth for flow attenuation is the inability of the plastic materials used to provide lasting sharp edges. As mentioned earlier, the flow attenuation provided by a labyrinth results primarily from turbulence generated by the baffles. It is well known that turbulence is induced much more effectively by sharp-edged obstructions. However, the plastic materials used for conventional labyrinth devices cannot be produced with highly sharp edges, and they rapidly become further rounded by the effects of the fluid flow during use. The low efficiency of the resulting labyrinths requires the use of greatly extended flow paths to achieve a given degree of attenuation.
There is therefore a need for a flow regulator which would provide substantially constant output over a wide range of input pressures and which would avoid the limitations associated with use of elastomeric materials.
SUMMARY OF THE INVENTION
The present invention is a flow regulator which employs a flow-attenuating labyrinth formed by a plurality of baffles, at least some of the baffles being implemented as leaf-spring portions. This configuration provides a number of advantages. Firstly, each leaf-spring portion is configured to be deflected by the pressure of the inlet-side fluid flow in a manner to provide localized independent fluid flow regulation. By combining a number of similar cells in series, highly effective overall regulation is obtained. According to a preferred feature, the leaf-spring portions are implemented as metallic elements, providing much sharper edges, and thus greater turbulence, than can be achieved in a plastic labyrinth. This allows the use of a much shorter and more compact labyrinth structure.
Thus, according to the teachings of the present invention there is provided, a flow regulator for regulating flow of a fluid, the flow regulator comprising: (a) at least one spring element; and (b) at least one flow-path-defining element configured to provide at least one fixed surface which cooperates with the at least one spring element to define a fluid flow path from an inlet passing through at least one flow regulating cell to an outlet, the at least one flow regulating cell including: (i) a leaf-spring portion provided by the at least one spring element, the leaf-spring portion having a front surface exposed to fluid flowing along the fluid flow path, the leaf-spring portion further providing an edge, the leaf-spring portion being elastically deflectable under pressure applied on the front surface by the fluid from an initial state to a deflected state, and (ii) a clearance surface provided by the at least one flow-path-defining element, the clearance surface defining, together with the edge of the leaf-spring portion, a variable clearance through which the fluid flow path passes, such that the leaf-spring portion is responsive to the pressure of the fluid adjacent to the front surface to vary the clearance, thereby regulating the flow of the fluid.
According to a further feature of the present invention, the at least one flow regulating cell defines a local flow path passing from adjacent to the front surface of the leaf-spring portion around the edge, thereby tending to produce turbulent flow.
According to a further feature of the present invention, the at least one flow regulating cell is configured such that deflection of the leaf-spring portion from the initial state through a predefined normal range of deflection gradually decreases the clearance, while deflection of the leaf-spring portion beyond the normal range of deflection increases a distance of the edge from the clearance surface.
According to a further feature of the present invention, the at least one flow regulating cell is implemented as a series of at least two flow regulating cells deployed sequentially along the fluid flow path.
According to a further feature of the present invention, the at least one spring element is implemented as a generally sheet-like element, the at least one leaf-spring portion being implemented as at least one tongue formed so as to project from the sheet-like element. The generally sheet-like element is preferably formed from metallic material, most preferably from a sheet of spring steel.
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Eureka Technologies LTD
Friedman Mark M.
Ganey Steven J.
Scherbel David A.
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