Fluid handling – Line condition change responsive valves – With separate connected fluid reactor surface
Reexamination Certificate
2002-12-30
2004-11-23
Hepperle, Stephen M. (Department: 3753)
Fluid handling
Line condition change responsive valves
With separate connected fluid reactor surface
C137S508000
Reexamination Certificate
active
06820643
ABSTRACT:
SUMMARY OF THE INVENTION
The present invention relates to a regulator of liquid pressure of the type used in liquid conducting systems, for example, irrigation systems with the pressure regulator maintaining a constant pressure of the liquid flowing out through it, independent from the inflowing pressure. The pressure regulator device in accordance with the present invention, apart from keeping the outlet pressure constant by-means of an adjustment of one of its components, the device works also as an antidrainage valve.
The liquid pressure regulator has five components: three main parts and two accessories. The main parts include a first part through which the liquid flows into the regulator; an intermediate part, a plunger which slides on a piston fixed on the first part, and a third part through which the liquid flows out of the regulator. The accessories include one seal and one spring.
It is important to note that the double frustoconical profile in the plunger and toroidal in the contact point of the plunger in the inlet piece and a bolt in which the plunger ends, which slides into the cylindrical cavity of the housing, giving a second support to get a coaxial sliding of the plunger on the fixed piston of the inlet part. Apart from these components, there is an alternative related to the plunger, on which a double rear bolt is foreseen: one of them is the one mentioned before, but concentric, and before this one, another bigger one is built, which leans on the internal wall of the housing and avoids liquid leakage until the desired pressure is obtained. With this, the regulator does double work: the pressure regulating valve and antidrainage valve simultaneously function, as was mentioned before.
BACKGROUND OF THE INVENTION
The pressure regulator most frequently used today differ substantially from the present invention, such prior art regulators are described in U.S. Pat. Nos. 4,543,985, 5,257,646 and 5,875,815. The technical differences between the prior art regulators and the present invention are, among other things, provided by the location where the regulation of the pressure is produced. In the prior art regulators, the liquid enters the regulator through the center and is directed to the periphery by means of a deflector star which immediately diverts to the center where the regulation takes place. During the first step, the central flow moves to the periphery, and in the second step, this same flow moves from the periphery back to the center where the regulation takes place. However, the prior art regulators are significantly more complex than the present invention because they have, on average, a total of least 18 components.
In the present invention, regulation takes place during the first step when the liquid flow moves from the center to the periphery of the regulator. The liquid flow moves back to the center only when leaving or exiting the device. This fluid flow path permits the present invention to be significantly less complicated and less costly than the prior art regulators while being highly effective and efficient.
In U.S. Pat. No. 5,875,815, a pressure regulating valve is provided with a built-in antidrainage device, but, as it will be explained later, such a valve differs substantially from the present invention, including everything related to the antidrainage device. Apart from what was previously mentioned related to the central flow of this regulator, in U.S. Pat. No. 5,875,815, the antidrainage device presents the following characteristics: the plunger, or cylindrical central part, must be built in three parts; the element working as the antidrainage device is positioned permanently in the center of the flow of the fluid, which means that even after the regulator permits the fluid into the device, the antidrainage elements continue to oppose the fluid flow, thereby producing high pressure losses. In the regulator in accordance with the present invention, on the contrary, the drainage system provides that: the plunger is always built in only one piece; and the more the plunger slides within the regulator assembly, the less the plunger opposes the fluid flow, unexpectedly decreasing the pressure losses within the device.
Prior art regulators are additionally disclosed in U.S. Pat. Nos. 4,474,207 and 2,888,033. The regulators in accordance with these patents are not frequently used today because they provide inaccurate pressure regulation due to the non-coaxial sliding of the intermediate cylindrical piece with respect to the inlet piece and due to the point of contact between the plunger and the inlet piece being flat on both pieces.
One important factor affecting inaccuracy of pressure regulation is that because there is a single supporting point between the plunger and the fixed piston, the axis of the plunger is unstable and, therefore, it does not move in a coaxial manner with respect to the fixed piston of the inlet piece. This produces lateral movements or inclination. Thus, the non-coaxial movement of the cylindrical piece produces a lack of accuracy of the regulator and a high level of hysteresis.
With respect to the lack of accuracy of this type of regulator, when the axis of the plunger does not have a coaxial and aligned position with respect to the axis of the piston, the closing of the plunger over the inlet piece is not consistent around the entire perimeter and, therefore, there are pressure leaks from the inlet to the outlet resulting in the regulator being inaccurate. Further, these differences are not constant, so for the same inlet pressure, there are different outlet pressures and, therefore, inaccuracy results from this type of regulator.
With respect to hysteresis, hysteresis may be observed when the performance of the regulator is represented on a graph in which the x-axis is the inlet pressure of the regulator and the y-axis the outlet pressure of the regulator. Two curves are obtained as the inlet pressure is varied. One curve results from the increase of the inlet pressure while the other curve is obtained as this pressure decreases. The difference between these two curves is called hysteresis, as shown in Graph No. 1. The upper curve was obtained by increasing the pressure in the inlet of the regulator, while the lower curve was obtained while decreasing the pressure in the inlet of the regulator. All pressure regulators have hysteresis, but the lower the hysteresis, the more efficient the regulator will be.
However, when the movement between the plunger and the piston is not coaxial, it is difficult for the plunger to return to its original position, thus increasing the hysteresis of the regulator. To overcome these problems, U.S. Pat. No. 2,888,033 suggests a screw structure which fixes the position of the plunger thereby causing an inclination of this piece from its initial position. Also, U.S. Pat. No. 4,474,207 discloses the use of additional ribs on the housing. These ribs provide very little space (almost none) over the plunger to be effective, a structure which increases the level of hysteresis. However, if a larger space is left to decrease the level of hysteresis, lateral movements cannot be avoided.
Also, the surfaces of contact between the plunger and the inlet piece of the present invention are flat. U.S. Pat. Nos. 4,474,207 and 2,888,033 share this structural characteristic. However, the problem of accuracy occurs when flow is low because there needs to be a small and accurate closing. In this operating condition, it is found that the change of pressure from the inlet to the outlet pressure does not occur in a single point. This change in pressure occurs throughout the thickness of the plunger. This means that there is an inlet pressure on one side of the plunger and an outlet pressure on the other side of the plunger. Consequently, if the closing is flat, the decrease of the pressure from the inlet to the outlet is progressive throughout the length or thickness of that plane. This means that there is an intermediate pressure between the inlet pressure and the outlet pressure and, therefore, this interm
Emrich & Dithmar LLC
Hepperle Stephen M.
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