HYDRO-PNEUMATIC PRESSURE VESSEL AND DIAPHRAGM ASSEMBLY METHOD

Abstract

An expansion tank for at least temporarily storing a pumped liquid under pressure, the including a thin wailed outer shell and a diaphragm located internally of the tank, and sealingly secured to the inner surface of the shell of the tank to divide the internal volume of the tank into a fluid-tight section for holding a gas under pressure and a fluid-tight section for holding a liquid under pressure. The diaphragm has an enlarged lip around the outer circumference of the diaphragm and being is connected to the interior portion of one of the substantially cylindrical sections via the enlarged lip being fitted tightly into a coupling ring, which in turn presses the enlarged lip of the diaphragm sealingly, circumferentially against the inner circumferential surface of the tank wall when the outer circumferential surface of the coupling ring is sealingly connect to the inner wall surface of one of the tank segments, sealing the enlarged lip against the inner surface of the tank. The tank segments are not finally assembled until after the diaphragm is sealed against the tank wall, so that the diaphragm divides the interior volume of the tank into two mutually fluid tight volumes that can be rendered fluid tight with respect to the space outside of the tank walls.

Claims

1. An expansion tank for at least temporarily storing a pumped liquid under pressure, the expansion tank comprising a thin walled outer shell and a diaphragm located internally of the tank and sealingly secured to the inner surface of the shell of the tank to divide the internal volume of the tank into a fluid-tight section for holding a gas under pressure and a fluid-tight section for holding a liquid under pressure; the expansion tank being formed from separate segments including at least two partially cylindrical, dome-shaped sections joined together to form the completed tank; the diaphragm having an enlarged lip around the outer circumference of the diaphragm and being sealingly connected to the interior portion of one of the substantially cylindrical sections via the enlarged lip at the outer circumference of the diaphragm; and a coupling ring having an inner and an outer circumferential surfaces, the outer circumferential surface including a depression extending completely around the circumference wherein the outer edges of the depression are separated by a distance not greater than the vertical dimension of the enlarged lip and the depression being sufficiently large to encompass the enlarged lip of the diaphragm; the coupling ring being fabricated independent of the tank segments and the enlarged lip of the diaphragm being sealingly, circumferentially connected between the inner circumferential surface of the tank wall and the outer circumferential surface of the coupling ring; wherein the completed tank was formed by first connecting the coupling ring to the diaphragm, then sealingly connecting the coupling ring to the inner wall surface of one of the tank segments, sealing the enlarged lip against the inner surface of the tank, and then finally assembling the tank segments such that the diaphragm is sealed within the tank walls and the diaphragm divides the interior volume of the tank into two mutually fluid tight volumes that can be rendered fluid tight with respect to the space outside of the tank walls.

2. The expansion tank of claim 1 wherein the coupling ring comprises a substantially level surface facing radially inwardly from the tank wall and the opposing face comprises at least one flap partially extending across the opening to the depression for holding in a sealing connection the enlarged lip of the diaphragm against the inner surface of the tank wall, the outer surface of the flap and the surrounding surface of the ring being sealingly connected to the inner surface of the tank wall.

3. The expansion tank of claim 1, further comprising an exterior wrap of resin-impregnated fiber winding.

4. The expansion tank of claim 1, wherein the diaphragm-coupling ring seal position may be infinitely adjustable along the length of the cylindrical portion of the tank to allow for the formation of an ideal water chamber-to-air chamber ratio.

5. The expansion tank of claim 1, wherein the outer shell and the coupling ring are formed of mutually compatible thermoplastic materials.

6. The expansion tank of claim 5, wherein the enlarged lip of the diaphragm is in the shape of an O-ring.

7. The expansion tank of claim 6, wherein one of the dome-shaped end pieces of the tank includes a sealable water inlet opening and the seal ring further comprising a stress relieving member extending axially outwardly from the depression towards the water inlet opening.

8. A method for forming an expansion tank for at least temporarily storing a pumped liquid under pressure, the expansion tank comprising a thin walled outer shell having two domes, one at each end of the tank and a central cylindrical section; and a flexible diaphragm located internally of the tank and secured to the inner surface of the tank to divide the internal volume of the tank into a fluid-tight section for holding a gas under pressure and a fluid-tight section for holding a liquid under pressure, wherein the diaphragm comprises an enlarged circumferential lip extending around the entire outer circumferential edge of the diaphragm, the method comprising: separately providing the two dome-shaped end segments for forming the enclosed tank; providing a circumferential coupling ring sized to fit tightly within and be secured to the interior wall surface along the central cylindrical section of the tank, the outer circumferential edge of the coupling ring being formed into a mouth, sized to tightly hold the enlarged circumferential lip of the diaphragm; securing the outer circumferential edge of the coupling ring to the inner circumferential surface of the central cylindrical section, such that the open side of the mouth portion of the coupling ring sealably holds the diaphragm lip against the internal surface of the tank; and combining the tank segments to form a thin-walled tank wherein the diaphragm is sealingly located internally of the tank walls to separate the inner tank volume into two mutually fluid-tight volumes for holding a liquid and a gas, respectively under pressure.

9. The method of claim 6 wherein the diaphragm and the coupling ring are separately formed and the circumferential, peripheral edge of the diaphragm is then sealingly secured in the mouth of the coupling ring.

10. The method of claim 6 wherein the diaphragm is separately formed and the coupling ring is then formed around circumferential, peripheral edge of the diaphragm so as to firmly secure the circumferential, peripheral edge of the diaphragm in the mouth of the coupling ring.

11. The method of claim 6 wherein the diaphragm is separately formed and the coupling ring is then formed around the circumferential, peripheral edge of the diaphragm so as to sealingly secure the circumferential, periph-eral edge of the diaphragm in the mouth of the coupling ring.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Having thus described the presently disclosed subject matter 5 in general terms, reference will now be made to the accompanying Drawings, which are not necessarily drawn to scale, and wherein:

[0013] FIG. 1 illustrates an elevation view of a hydropneumatic filament wound pressure vessel (herein referred to as an “FRP tank”);

[0014] FIG. 2 illustrate is a cross-sectional view, the plane of section being indicated by the line 2-2 in FIG. 1;

[0015] FIG. 3 illustrates an enlarged cross-sectional view showing details of the seal area between the seal ring, tank liner sidewall, and the flexible diaphragm in an assembled state;

[0016] FIG. 4 illustrates an enlarged cross-section view of the seal profile on the flexible diaphragm before it is installed into the tank liner;

[0017] FIG. 5 illustrates an exploded view of the FRP tank before it is assembled and when it is applied to a split shell tank liner;

[0018] FIG. 6 illustrates an exploded view of the FRP tank before it is assembled and when it is applied to a three (3) piece injection molded domes and extruded sidewall tank liner;

[0019] FIG. 7 illustrates a cross section of the flexible diaphragm and seal ring preassembled before it is inserted into the tank liner;

[0020] FIG. 8 illustrates an enlarged cross-section of the seal ring and flexible diaphragm seal profile before it is inserted into the tank liner, as well as the stress reliever to reduce stress on the seal area during operation;

[0021] FIG. 9 illustrates an enlarged cross-section of the seal ring and flexible diaphragm after it is inserted into the tank liner, and showing the surface to surface contact between the seal ring and the tank liner;

[0022] FIG. 10 illustrates an enlarged cross-sectional view of the seal ring and flexible diaphragm permanently installed in the tank liner after the seal ring is welded to the tank liner sidewall; and

[0023] FIG. 10A illustrates the enlarged cross-sectional view of the seal ring and flexible diaphragm when the tank is under water pressure in the water side of the diaphragm and the diaphragm is exerting pressure against the stress relieving members of the coupling ring.

[0024] FIG. 11 is a partial cross-sectioned view of the seal ring, including the radial enforcement ribs at the top of the ring.

DETAILED DESCRIPTION

[0025] The presently disclosed subject matter now will be described more fully hereinafter with reference to the accompanying Drawings, in which some, but not all embodiments of the presently disclosed subject matter are shown. Like numbers refer to like elements throughout. The presently disclosed subject matter may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Indeed, many modifications and other embodiments of the presently disclosed subject matter set forth herein will come to mind to one skilled in the art to which the presently disclosed subject matter pertains having the benefit of the teachings presented in the foregoing descriptions and the associated Drawings.

[0026] Therefore, it is to be understood that the presently disclosed subject matter is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. In an embodiment, the presently disclosed subject matter provides a fiberglass reinforced plastic pressure tank made with a plastic tank liner, a flexible, preferably rubbery, diaphragm and reinforced with a composite fiberglass/resin matrix. This type of tank is also known as a hydro-pneumatic filament wound pressure vessel (herein referred to as an “FRP tank”). The invention is generally used for residential and commercial water storage and water delivery applications requiring pressurized water. The described invention is an FRP tank and method for providing a low cost, reliable and repeatable method for installing a flexible diaphragm into the FRP tank.

[0027] Referring now to FIGS. 1-11, the present invention includes, in one embodiment, an FRP tank 100 that includes a plastic liner 105 with at least one axial opening 107. The FRP tank 100 may be reinforced with continuous strand fiberglass and further includes a flexible internal diaphragm assembly 110, that is preferably elastic or rubbery, (which is, typically, an elastomer or flexible thermoplastic). The plastic liner 105 can preferably be made of any rigid thermoplastic material suitable for use in potable water applications.

[0028] The flexible diaphragm 110, when installed in the plastic liner 105, forms two (2) hermetically sealed and independent chambers 115 as required for the FRP tank 100 application. The flexible diaphragm 110 may be positioned at any point along the cylindrical sidewall 120 of the FRP tank 100. The diaphragm 110 can be formed of a material comprising, by way of example only, a polymer, elastomer, rubber, RTV, or thermoplastic, or multiple layers compromising the same. In certain preferred embodiments, the diaphragm 110 comprises butyl rubber or EPDM. In other embodiments, the diaphragm may be filled with solids such as but not limited to particles or flakes of polymers or minerals including glass, talc, carbon and graphite; chopped fibers, discontinuous fibers, short or long fibers, or continuous fibers of polymers or minerals including glass or carbon; nanocomposites; clays; or other fibers, particles, flakes or hollow microspheres; or woven or non-woven fabrics; to improve the thermomechanical properties or decrease permeability of gases through the membrane. In some embodiments, multiple layers of the diaphragm can be bonded, but the layers can also be non-bonded. In certain embodiments, the layers include a thin, higher modulus layer supported by a thicker, lower modulus layer. The higher modulus layer can be selected from chemically resistant polymers, or polymers preferred for contact with potable water, such as polypropylene, polyethylene, polybutylene, or the like. The low modulus layer may be selected for different properties, such as durability, toughness, and low cost, protected from contact with the potable water by the high modulus layer.

[0029] The plastic liner 105 is preferably presented in a form that allows internal access prior to final application of the continuous strand fiberglass, such as a split shell injection molded liner or using one or a pair of unassembled injection molded domes 125 and extruded sidewall 120 plastic tank liner portion. The plastic tank liner 105 may also be a blow molded liner that has been cut around the circumference to allow internal access. The individual sections of the tank liner 105 and of the seal ring are preferably formed of non-metallic materials, selected from the group including preferably rigid thermoplastic polymers, whether plastic or elastomeric, or multilayer materials comprising the same; such as a group of thermoplastics including polyolefins, polyethylene, polypropylene, polybutylene, nylon, PVC, CPVC, ionomers, fluoropolymers, copolymers, crosslinked polyolefins such as crosslinked polyethylene (PEX, PEX-a. PEX-b, PEX-c or XLPE), or multilayer structures comprising the same. Although multiple incompatible layers can be used, layers formed of incompatible materials can preferably include a “tie layer” which is usually one or a combination of two or more mutually compatible materials that form a bonding layer between two mutually incompatible materials. Tie layers can include, for example, a thermoplastic material that provides adhesion to two adjacent materials, most often through melt processing or chemical reactions; modified acrylic acid, or anhydride grafted polymers or those similar to but not limited to DuPont's Bynel, Nucrel, and Fusabond grades, or those described and referenced, as further examples, in U.S. Pat. Nos. 8,076,000, 7,807,013 and 7,285,333. The melting point or melt index of the tie layer can be selected so that the tie-layer can be post-processed without substantially melting or flowing other non-metallics in the structure.

[0030] The FRP tank 100 may further include a seal ring 130 that captures, in a seal profile 135 of the enlarged circumferential lip 135 of the flexible diaphragm 110, in a depression in its outer circumference. The outer circumference of the seal ring 130 can be secured to the cylindrical sidewall 120 of the plastic liner 105. The seal ring 130 preferably provides three (3) sides of the required seal containment while the tank liner 105 provides the 4th side of the seal containment. The seal ring 130 can be attached to the sidewall 120 of plastic liner 105 using any known/suitable industry standard welding methods such as, for example, spin welding, ultrasonic welding, and laser welding, or using compatible and inert adhesives. The seal ring 130 may further include a primary stress reliever 140 and a secondary stress reliever 141, both built into the seal ring 130 to reduce stresses on the seal profile 130 when water pressure in the chamber under the diaphragm causes the diaphragm to stretch out, as shown in FIG. 10A, during operation of the FRP tank 100. This can cause the circumferential lip 140 to flex radially inwardly to relieve stress on the diaphragm seal.

[0031] The seal ring 130 preferably provides a durable seal creating two (2) hermetically sealed chambers 115 of the FRP tank 100, and wherein the seal point may be located at any position along the sidewall 120 of the FRP tank 100. Further, the seal created by seal ring 130 provides a seal that can expand and contract with the pressure variations the 105 may also then be sealed together using known suitable industry standard welding or adhesive methods.

[0032] In another example, a diaphragm assembly method may include providing an unassembled three (3) piece tank liner 105 including dome portions 125 (e.g. an upper dome and a lower dome) and a sidewall 120 tank liner portion. Prior to assembling the three (3) piece tank liner 105, the flexible diaphragm 110 can be preassembled to the seal ring 130, for example, as shown in FIGS. 7 and 8. Preassembled flexible diaphragm 110 and seal ring 130 can then be inserted into the tank liner 105 and attached to the sidewall 120 using any known/suitable industry standard welding methods such as, for example, spin welding, ultrasonic welding, and laser welding. The upper and lower dome portions 125 may then be sealed to their respective upper and lower portions of the sidewall 120 using known/suitable industry standard welding methods.

[0033] The present invention provides a seal for the flexible diaphragm 110 that reduces the part count and processing cost over previous known sealing methods, provides a sealing method that eliminates the use of non-plastic crimping rings, and utilizes a proven and highly reliable ‘O” Ring sealing method to create the hermetically sealed chambers 115.

[0034] Following long-standing patent law convention, the terms “a,” “an,” and “the” refer to “one or more” when used in this application, including the claims. Thus, for example, reference to “a subject” includes a plurality of subjects, unless the context 20 clearly is to the contrary (e.g., a plurality of subjects), and so forth.

[0035] Throughout this specification and the claims, the terms “comprise,” “comprises,” and “comprising” are used in a non-exclusive sense, except where the context requires otherwise. Likewise, the term “include” and its grammatical variants are intended to be non-limiting, such that recitation of items in a list is not to the exclusion of other like 25 items that can be substituted or added to the listed items.

[0036] For the purposes of this specification and appended claims, unless otherwise indicated, all numbers expressing amounts, sizes, dimensions, proportions, shapes, formulations, parameters, percentages, quantities, characteristics, and other numerical values used in the specification and claims, are to be understood as being modified in all 30 instances by the term “about” even though the term “about” may not expressly appear with the value, amount or range. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are not and need not be exact, but may be approximate and/or larger or smaller as desired, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in the art depending on the desired properties sought to be obtained by the presently disclosed subject matter. For example, the term “about,” when referring to a value can be meant to encompass variations of, in some embodiments, ±100% in some embodiments ±50%, in some embodiments ±20%, in some embodiments ±10%, in some embodiments ±5%, in some embodiments ±1%, in some embodiments ±0.5%, and in some embodiments ±0.1% from the specified amount, as such variations are appropriate to perform the disclosed methods or employ the disclosed compositions.

[0037] In one example, a diaphragm assembly method can include providing an unassembled split shell tank liner 105. Prior to assembling the split shell tank liner 105, the flexible diaphragm 110 may be preassembled to the seal ring 130, for example, as shown in FIGS. 7 and 8. Preassembled flexible diaphragm 110 and seal ring 130 may then be inserted into the tank liner 105 and attached to the sidewall 120 of plastic liner 105 using any known/suitable industry standard welding methods such as, for example, 30 spin welding, ultrasonic welding, and laser welding. The split shell portions of tank liner 105 may also then be sealed together using known/suitable industry standard welding methods. In another embodiment, the parts can be sealed together using a suitable, inert but compatible adhesive

[0038] Further, the term “about” when used in connection with one or more numbers or numerical ranges, should be understood to refer to all such numbers, including all numbers in a range and modifies that range by extending the boundaries above and below the numerical values set forth. The recitation of numerical ranges by endpoints includes all numbers, e.g., whole integers, including fractions thereof, subsumed within that range (for example, the recitation of 1 to 5 includes 1, 2, 3, 4, and 5, as well as fractions thereof, e.g., 1.5, 2.25, 3.75, 4.1, and the like) and any range within that range,

[0039] Although the foregoing subject matter has been described in some detail by way of illustration and example for purposes of clarity of understanding, it will be understood by those skilled in the art that certain changes and modifications can be practiced within the scope of the appended claims.