US20080017653A1 - Vessel diaphragm and method - Google Patents

Abstract

An elastic thermoplastic diaphragm for use in a vessel having an inner surface. The vessel includes a liner that has an inner liner surface and first and second ends. A first endcap is secured to the liner first end and a second endcap to the liner second end. The diaphragm is secured to the inner vessel surface and seals along a peripheral edge to the vessel inner surface so as to define a volume inside the vessel. The diaphragm can flex, and thereby increase or decrease the volume.

Description

BACKGROUND OF THE INVENTION
• 1. Field of the Invention
• The present invention relates generally to a diaphragm and more specifically to a thermoplastic diaphragm assembly for use in a pressure vessel.
• 2. Discussion of Related Art
• A water system, for example a well water system, typically includes a pneumatic accumulator tank, a pump, and a water source. In a base form, the pneumatic accumulator tank receives water from the water source. A quantity of air pressurizes the pneumatic accumulator tank. The pneumatic accumulator tank retains the air in the tank and supplies pressurized water to the water supply system. Thus, it is not necessary for the pump to continuously pressurize the water supplied to the tank; the water provided to the water supply system is pressurized by the air in the tank.
• A diaphragm separates the air and water in the pneumatic accumulator tank. A traditional diaphragm includes a bag formed from cup-shaped halves that can either stretch or unfold to receive the air. In such a traditional accumulator tank, the tank itself is formed from a pair of metal shells, and mating ends of the cup-shaped diaphragm halves are clamped between the metal shells to mount the diaphragm to the tank and seal the diaphragm.
• Normally, water is introduced into the diaphragm, and air is introduced into the remaining volume of the tank. Accordingly, a water inlet to the diaphragm is formed in an end wall of the tank. The diaphragm isolates the water from the metal walls of the tank, and thereby prevents corrosion of the tank. However, in the past it has been difficult and expensive to secure the diaphragm within the tank. It has been especially difficult to assembly and seal the water inlet to the diaphragm. Therefore, there exists a need in the art for an improved diaphragm water inlet structure that facilitates assembly and reliably seals the diaphragm water inlet.
• Moreover, the traditional diaphragm assembly is expensive and not adapted for economical use in non-metal tanks, such as thermoplastic composite pressure vessels. Therefore, there exists a need in the art for an improved diaphragm assembly that is adapted for use in thermoplastic pressure vessels.
SUMMARY OF THE INVENTION
• The present invention is directed toward an improved diaphragm water inlet structure that facilitates assembly and sealing of the diaphragm to the pressure vessel. The present invention is further directed toward an improved thermoplastic diaphragm that is adapted for use in a thermoplastic composite pressure vessel.
• In accordance with one embodiment of the present invention, a first diaphragm is bowl-shaped and has an open end that is surrounded by a peripheral edge. The peripheral edge is sealed to an inner surface of the pressure vessel and defines an enclosed space for receipt of fluid, such as water. The diaphragm and pressure vessel are formed of compatible thermoplastic material to permit sealing or heat welding of the diaphragm to the pressure vessel.
• In further accordance with the present invention, the pressure vessel includes a cylindrical liner having end caps secured to first and second ends thereof. The liner is preferably formed from a thermoplastic material and may be formed by known techniques, such as extrusion, injection molding, and the like. The end caps are preferably formed from a composite material including a first or inner layer of thermoplastic and a second or outer reinforced layer, which preferably comprises of intermixed thermoplastic and glass fiber materials.
• In further accordance with the present invention, the diaphragm may be sealed to the liner, one of the end caps, or may be sealed between a junction of the liner and one of the end caps. The diaphragm peripheral edge may include a sealing ring to facilitate sealing and securing of the diaphragm to the liner or end cap. Alternatively, the diaphragm may be directly secured to the liner or end cap.
• In further accordance with the present invention, the diaphragm includes first and second cup-shaped diaphragm portions. The first and second diaphragm portions are sealingly secured to one another at their open ends. At least one of the first and second diaphragm portions is sealing secured to at least one of the vessel end caps or the vessel liner, as described hereinbefore.
• The first diaphragm portion extends into the tank and away from one end cap and expands and contracts in use. The second diaphragm portion overlies the one end cap and is relatively stationary in use. An inlet to the diaphragm is formed in the one end cap and the second diaphragm portion by means of which fluid may be introduced into the diaphragm. The second diaphragm portion is stationary in use, and may be formed from a relatively stiffer material than the elastic first diaphragm portion.
• In further accordance with the present invention, an inlet assembly is provided to seal the diaphragm inlet and sealingly secure the diaphragm to the end cap. The inlet assembly includes a seat and a fitting, and the diaphragm includes a sealing ring. The end cap, seat, and the sealing ring each define coaxial or aligned apertures, and the fitting extends through the apertures. The seat and the fitting cooperate to define a ring-shaped groove that sealing captures the sealing ring.
• In further accordance with the present invention, a fitting is formed from a thermoplastic material and is welded or heat-sealed to the endcap at the water inlet to seal the fitting to the water inlet. The fitting may also be welded or heat-sealed to the diaphragm so as to seal the fitting to the diaphragm.
BRIEF DESCRIPTION OF THE DRAWINGS
• These and further features of the invention will be apparent with reference to the following description and drawings, wherein:
• FIG. 1 is a cross-sectional side view of an apparatus according to a first embodiment of the invention;
• FIG. 2 is a cross-sectional side view of an apparatus according to a second embodiment of the invention;
• FIG. 3 is a cross-sectional side view of an apparatus according to a third embodiment of the invention;
• FIG. 4 is a cross-sectional schematic side view of part of the apparatus shown inFIG. 3;
• FIG. 5 a cross-sectional schematic side view of part of the apparatus shown inFIG. 3;
• FIG. 6 is a schematic cross-sectional view of a diaphragm subassembly according to the present invention;
• FIG. 7 is a schematic cross-sectional view of a pressure vessel incorporating a diaphragm according to the present invention; and,
• FIG. 8 is an enlarged cross-sectional view of a fitting disposed within a vessel ofFIG. 7 incorporating the diaphragm assembly ofFIG. 6;
• FIG. 9 is an enlarged cross-sectional view of the fitting used in the vessel ofFIG. 7.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
• Apressure vessel100 according to a first embodiment of the present invention is shown inFIG. 1. Thevessel100 includes acylindrical liner102, and first andsecond endcaps104,106. Thecylindrical liner102 has anouter surface110 and aninner surface114. Theliner102 defines anaxis108 and has opposing ends. Thefirst endcap104 is secured to a first end of theliner102, and thesecond endcap106 is secured to a second end of theliner102. Theliner102 cooperates with the end caps to define aninterior volume116 of thevessel100.
• Theliner102 andendcaps104,106 are formed from a thermoplastic material. More specifically, theendcaps104,106 are generally identical and include a first,inner layer104a,106aand a second,outer layer104b,106b. Thefirst layer104a,106ais formed from a thermoplastic material, such as polypropylene or polyethylene, while thesecond layer104b,106bis formed from a reinforced thermoplastic, such as a commingled glass and thermoplastic material, as will be described more fully hereinafter. Theliner102 is preferably formed from a compatible thermoplastic material, such as polypropylene, to facilitate bonding of theendcaps102,104 thereto.
• Although theendcaps104,106 are preferably identical to one another and generally dome-shaped, it is contemplated that the endcaps may be frusto-conical or flattened, and that the endcaps need not be alike. Moreover, the endcaps may be of any desired shape or size.
• Theendcaps104,106 are secured to first and second ends of theliner102 at respective first andsecond transition areas103a,103b. Theendcaps104,106 are secured to theliner102 at thetransition areas103a,103bby laser welding, hotplate welding, spin welding, or equivalent techniques known in the art of thermoplastic material joining or fabrication, so as to define an integrated or unitary structure. In a preferred embodiment, the endcapfirst layer104a,106aextend axially beyond the endcapsecond layer104b,106b, as illustrated, so as to define a steppedopen end136 of theendcap104,106 that is welded, preferably by laser welding or infrared welding, to theliner110. Although laser welding or infrared welding to integrally secure or bond theendcaps104,106 to theliner102 is currently preferred, it is contemplated that alternative methods of attachment, such as spin welding, hot plate welding, solvent welding, etc., may be used without departing from the scope and spirit of the present invention.
• Thesecond layer104b,106bis preferably a thermoplastic and oriented or non-oriented glass fiber composite layer. Preferably, thesecond layer104b,106bis formed from a commingled thermoplastic and glass fiber fabric sold as TWINTEX, commercially available from Saint-Gobain Vetrotex America Inc. (Valley Forge, Pa.). In this embodiment, the glass fibers are woven and in the form of a fabric mat, and in alternative embodiments, the oriented fibers are biaxial, triaxial, looped, and/or stitched. In the preferred and illustrated embodiment, the first and second layers of theendcap104,106 are integrally secured to one another, such as by insert molding or compression molding, so as to define a unitary or integral endcap structure.
• Anoverwrap layer109 is wound onto theliner102 and over thetransition areas103a,103bso as to extend over edges of the first andsecond endcaps104,106 adjacent theliner102. Theoverwrap layer109 is a continuous glass filament thermoplastic composite layer (i.e., commingled glass and thermoplastic fibers) that is heat sealed to theliner102. These fibers are like the TWINTEX fibers that form the endcapsecond layers104b,106b, but are supplied in an endless or continuous format suitable for continuous filament winding. As noted hereinbefore, portions of theoverwrap layer109 preferably extend across thetransition areas103a,103band, accordingly, extend over a portion of the endcaps and overlie at least the free edges of theendcaps104,106. Insofar as the endcaps include the reinforcedsecond layers104b,106b, it is not considered necessary to wrap theoverwrap layer109 completely around theendcaps104,106.
• While in the preferred embodiment the overlap layer extends circumferentially around theliner102 and thetransition areas103a,103b, it is contemplated that theoverwrap layer109 may, instead, be helically wrapped around theliner102 and theendcaps104,106. Further, it is contemplated that theendcaps104,106 only include the first layer (i.e., thenon-reinforced thermoplastic layer104a,106a) and that reinforcement of theliner102 and theendcaps104,106 be provided by the helically-wound glass andthermoplastic overwrap layer109. This later alternative is illustrated inFIG. 3 and discussed hereinafter.
• Moreover, in alternative embodiments described hereinafter, thecylindrical liner102 andendcaps104,106 are thermoset plastic or metal, for example stainless steel or aluminum.
• Thevessel100 receives a diaphragm that is formed from first and secondthermoplastic diaphragm portions120,122. Thefirst diaphragm portion120 is generally bowl or cup-shaped, and is formed from an elastomeric thermoplastic material. The term elastomeric thermoplastic material, as used herein, may be any thermoplastic elastomer (TPE), which refers to a diverse group of rubber-like materials including ethyl vinyl acetate (EVA), rubber, rubber blends, polypropylene-rubber blends, as well as materials such as those sold under the trademarks SANTOPRENE and TREFSIN by Advanced Elastomer Systems, Inc. A peripheral edge surrounds an open end of thefirst diaphragm portion120, and is integrally connected to aring128. Preferably, at least one of thefirst diaphragm portion120 and thering128 is formed from an elastomeric thermoplastic material that is compatible with the liner material so as to be easily joined to theliner102 or first endcapinner layer104aby the thermoplastic attachment techniques described hereinbefore. Moreover, thefirst diaphragm portion120 and thering128 are integral with one another so as to define a unitary structure. Naturally, thefirst diaphragm portion120 and thering128 may be formed at the same time, or may be manufactured separately and then joined to one another by the aforementioned thermoplastic welding techniques.
• Thering128 is disposed between the peripheral edge of thefirst diaphragm portion120 and an inner surface of thefirst endcap104, and is joined or sealingly secured to thefirst endcap104 at a first joint134. Preferably, the first joint134 is disposed at about the end of theliner102 to about the steppedopen end136 of thefirst layer104aof thefirst endcap104, which is generally at thetransition area103b.
• Thesecond diaphragm portion122 is also generally bowl-shaped and formed from a thermoplastic material. Thesecond diaphragm portion122, however, generally conforms to the shape of the inner surface of thefirst endcap104 over which it extends. The first andsecond diaphragm portions120,122 are sealed to one another at their open ends. In the preferred and illustrated embodiment the first andsecond diaphragm portions120,122 are in abutting engagement with one another. More specifically, the annular open end of thesecond diaphragm portion122 is in sealing engagement with thering128 and the annular open end of thefirst diaphragm portion120. Naturally, it is considered apparent that the free ends of thediaphragm portions120,122 may overlap, or that thering128 may be secured to peripheral edges of both the first and second diaphragm portions (i.e., between the inner surface of thesecond diaphragm portion122 and the outer surface of the first diaphragm portion120). Accordingly, the first andsecond diaphragm portions120,122 cooperate with one another to form a bag-like, elastically extendable receptacle separating theinterior volume116 of thevessel102 into a first ordiaphragm cavity140aand asecond cavity140b.
• Thediaphragm cavity140adefines a volume that can be varied. For example, thediaphragm cavity140ahas a reduced volume when thefirst diaphragm portion120 is in a collapsed condition, compared to an increased volume of thediaphragm cavity140awhen thefirst diaphragm portion120 is in an elastically extended or inflated condition. Due to its location adjacent thefirst endcap104, thesecond diaphragm portion122 will be generally stationary during extension and retraction of thefirst diaphragm portion120.
• Aninlet passageway144 is formed through thefirst endcap104 and thesecond diaphragm portion122 through which water may be introduced into thediaphragm cavity140a. In use, and as described more fully hereinafter, an inlet fitting is disposed through theinlet passageway144 so as to communicate fluid into and out of the diaphragm.
• Thesecond endcap106 is semi-hemispherical and dome-shaped, and defines anaperture160 through which anair valve assembly162 extends. Theair valve assembly162 is conventional in the pressure vessel art, and will not be discussed further hereinafter.
• In use, thesecond cavity140bis charged or pressurized to a predetermined pressure P1 by use of thevalve assembly162. Water is pumped into thediaphragm cavity140avia theinlet144 and stored in the diaphragm at a pressure P2, which is generally equal to the second cavity pressure P1. When water is required by the water supply system, pressurized water flows from the diaphragm through theinlet144 and an associated inlet/outlet valve (not shown), to the water supply system. As water flows out of the diaphragm, the diaphragm collapses and the pressures P1, P2 decrease. When the pressures P1, P2 reach a predetermined lower limit, the pump is actuated to introduce further water into thediaphragm cavity140a. When the pressures again return to a desired upper limit, the pump is deactivated.
• In the above-described embodiment, thesecond diaphragm portion122 isolates fluid from thefirst endcap104. Because thesecond diaphragm portion122 is adjacent to and coextensive with theinner layer104aof thefirst endcap104, it does not move or expand in response to the addition of the fluid to thediaphragm cavity140a. Accordingly, thesecond diaphragm portion122 may be formed of a relatively more rigid, and less expensive, material than the elastically expandablefirst diaphragm portion120, if desired. Moreover, since thefirst endcap104, and more specifically, theinner layer104aof thefirst endcap104, is formed from a water compatible thermoplastic material, thesecond diaphragm portion122 may be omitted, and the resulting diaphragm would only be formed from the extensible or elasticfirst diaphragm portion120. Such an assembly would reduce costs and provide for more efficient assembly and manufacture.
• When manufacturing thevessel100 depicted inFIG. 1, theliner110 andendcaps104,106 are separately formed. Thereafter, thediaphragm portions120,122 are installed in thefirst endcap104. Preferably, after thediaphragm portions120,122 are properly disposed relative to thefirst endcap104, thering128, which is held temporarily in place by a friction or interference-type fit, is sealingly secured to thefirst endcap104 by heat welding, laser welding, or other equivalent techniques, with laser welding being the currently preferred method. Thereafter, thefirst endcap104 with the diaphragm assembly attached thereto, is sealing attached to theliner102, and thesecond end cap106 is secured to the opposite end of theliner102. As noted previously, the first andsecond endcaps104,106 may be sealingly secured to theliner102 by conventional thermoplastic joining techniques such as spin welding, hot plate welding, laser welding, infrared welding, or the like, with laser welding and infrared welding being the currently preferred methods.
• Anothervessel200 according to the present invention is shown inFIG. 2. Thevessel200 has many parts that are substantially the same as thevessel100; this is indicated by the use of the same reference numerals inFIGS. 1 and 2. Theapparatus200 differs primarily in that it includes an alternative elasticthermoplastic diaphragm250.
• Thediaphragm250 is a semi-hemispherical and dome-shaped or bowl-shaped membrane that has aperipheral edge252 surrounding its open end. Theperipheral edge252 is secured to theinner surface114 of theliner102 at a location intermediate the first andsecond endcaps104,106. Thediaphragm edge252 is sealed to the linerinner surface252, preferably by heat sealing, or laser, infrared hot-plate or spin welding. Theperipheral edge252 may be slightly built up or enlarged relative to the remaining portions of thediaphragm250 to facilitate sealing and secure attachment thereof to theliner102. Alternatively, thediaphragm250 may include a peripheral ring, similar toring128 described hereinbefore, if desired. Thediaphragm250 cooperates with thefirst endcap104 and a portion of theinner surface114 to define adiaphragm cavity280 that receives water via the opening orinlet144.
• In accordance with the second embodiment, thediaphragm250 is secured to theliner102 at a predetermined position between the liner ends. Thereafter, theendcaps104,106 are secured to theliner102, as described hereinbefore, and theliner102 andtransition areas103a,103bare wrapped with theoverwrap layer109. Operation or use of the vessel illustrated inFIG. 2 is substantially identical to that of the vessel ofFIG. 1, and will not be described further hereinafter.
• With reference toFIGS. 3-5, avessel300 comprising a third embodiment of the invention is shown. Thevessel300 has many parts that are substantially the same as the previously describedvessels100,200; this is indicated by the use of the same reference numerals inFIGS. 3-5 as were used inFIGS. 1 and 2. Thevessel300 has afirst end302 and asecond end304, and includes aliner102, first andsecond endcaps104′,106′, ahelical overwrap layer319, and adiaphragm assembly310. Thediaphragm assembly310 is formed from an elastomeric thermoplastic material, such as described hereinbefore.
• Thefirst endcap104′ is attached at theliner102 so as to define afirst end302 of thevessel300, and has afirst aperture326 formed therein for receipt of an inlet assembly. Thesecond endcap106′ is attached to theliner102 so as to define thesecond end304 of thevessel300, and has asecond aperture328 formed therein for receipt of a valve assembly. The illustrated first andsecond endcaps104′,106′ each have only a single non-reinforced thermoplastic dome-shaped thermoplastic layer, similar to the first,inner layer104a,106adescribed hereinbefore. The reinforcement or strength of thevessel300 is primarily provided by theoverwrap layer319 that extends over theliner102 and around theendcaps104′,106′. Theoverwrap layer319 is formed from a commingled glass and thermoplastic layer, as described hereinbefore with regard to the overwrap layer119 ofFIGS. 1-2.
• Thediaphragm assembly310 includes afirst diaphragm portion336 and asecond diaphragm portion338. The first andsecond diaphragm portions336,338 are bowl-shaped and have free ends adjacent to theliner102 and in continuous contact with each other so as to form aseam340. A sealingring342 clamps the free ends of thediaphragms336,338 to seal the diaphragms together at theseam340. The free ends are somewhat enlarged and are captured by a sealingring342, which is preferably formed from a thermoplastic material so as to facilitate welding or attachment of thering342 to thediaphragm portions336,338, if desired. Alternatively, the free ends of the first andsecond diaphragm portions336,338 may be integrally sealed or fused to one another using the techniques described hereinbefore. Thefirst diaphragm portion336 has an annular sealing rib or O-ring344 that defines anaperture346 aligned with the aperture in thefirst endcap104′.
• With particular reference toFIG. 4, theinlet assembly350 at thefirst end302 of thevessel300 includes a ring-shapedseat354 and a fitting356. Thefitting assembly356 is adapted to receive anoutlet fitting358.
• The ring-shapedseat354 is integrally formed in thefirst endcap104′ and radially surrounds the endcap aperture. Preferably, theseat354 is insert molded in thefirst endcap104′. The ring-shapedseat354 includes a radially inwardly facingsurface360 that is aligned with thering aperture346 and defines a portion of the first endcap aperture. Theseat354 includes aradially extending flange364 that is encapsulated in or surrounded by thefirst endcap104′. Theflange364 includes projecting ridges that facilitate bonding or integrating of theflange364 with thefirst endcap104′ during molding thereof. As illustrated, portions of thefirst endcap104′ extend over each side of theflange364, thus sandwiching or encapsulating theflange364 within theendcap104′, as illustrated. Theseat354 further defines a first ring-shaped groove that surrounds the first endcap aperture and is open to the interior of thevessel300.
• The fitting356 has a radially flaredproximal end372 that is received within thevessel300, and a substantially tubular second portion that extends through thefirst seat aperture360. The second portion includes a threadeddistal end370 that is disposed outside thevessel300.
• The flaredfirst end372 of the fitting356 cooperates with the ring-shaped groove of theseat portion354 to define an annular recess that is adapted to theannular sealing rib344 of thediaphragm assembly310. Theseat portion354 and the flaredportion372 cooperate with each other to clamp thering344 in the annular recess and to thereby seal thediaphragm assembly310 to thefitting assembly350.
• The tubular second portion of the fitting356 has anannular groove374 formed therein, as illustrated. The ring-shapedgroove374 receives a C-shapedspring clip376, while the threadedportion370 is adapted to receive the outlet fitting orpipe358.
• During assembly, the diaphragmfirst portion336 is placed adjacent thefirst endcap104′, and the fitting356 is pushed through the aligned openings in thefirst diaphragm portion336 and thefirst endcap104′. Theannular sealing rib344 is trapped in the annular recess formed between the fitting356 and theseat portion354, and thespring clip376 is installed in thegroove374 to retain the fitting356 in place on thefirst endcap104′ and thereby prevents the fitting356 from being pulled back into the vessel. Thereafter, thefirst endcap104′ may be attached to theliner102, as described hereinbefore, and then thesecond diaphragm portion338 is sealing secured to thefirst diaphragm portion336. Subsequently, thesecond endcap106′ is attached to theliner102 such as by spin welding or laser welding, as described hereinbefore. The second endcap324 preferably includes an air valve assembly. Thereafter, theliner102 andendcaps104′,106′ may be helically wrapped with the overwrap layer319 (i.e., commingled glass and thermoplastic), as described hereinbefore. Alternatively, the endcaps may include a reinforcing outer layer, and only the liner and transition areas may be circumferentially wrapped with the overwrap layer, as discussed previously.
• With particular reference toFIG. 5, asecond endcap106′ at thesecond end304 of thevessel300 is shown to include a second ring-shapedseat384 and avalve386. The second ring-shapedseat384 is substantially identical to the first ring-shapedseat354, but has been machined in a different manner to facilitate attachment of thevalve386. More specifically, the second ring-shapedseat384 differs in that it includes a raisedcentral seat390 that is centered on theaxis320 and defines avalve aperture392. Thevalve386 extends through thevalve aperture392 and seals against the raisedcentral seat390.
• According to the present invention, prior to the assembly of thevessel300, theendcaps104′,106′ are identical, and integrally include theseats354,384. At this point theseats354,384 have a solid or continuous central portion. Endcaps that are to be used asfirst endcaps104′, as described hereinbefore, are machined so as to form thefirst aperture360 while endcaps that are to be used assecond endcaps106′ have a smaller opening, which becomes thevalve aperture392, drilled therein. Otherwise, the first andsecond endcaps104′,106′ are preferably identical.
• As briefly mentioned hereinbefore, during assembly of thevessel300, thefirst endcap104′ with the encapsulatedseat354 provided therein is provided. Theseat354 is machined so as to define thefirst seat aperture360, which is sized to accommodate the fitting356. The fitting356 is inserted through both the ring aperture in thefirst diaphragm336 and thefirst seat aperture360 in thefirst endcap104′. The sealingring344 of thefirst diaphragm336 is thus disposed in the annular recess defined by the ring-shaped grooves in theseat354 and the fitting356.
• Thespring ring376 is snapped into thegroove374 to hold the fitting356 in place. Thesecond diaphragm338 then is aligned with thefirst diaphragm336 so that the free ends of thediaphragms336,338 are in continuous contact with each other to define theseam340. Thering342 clamps the diaphragm free ends so as to seal thediaphragms336,338 together at theseam340. Thering342,liner102, andfirst endcap104′ are secured to one another using thermoplastic welding or attachment techniques described hereinbefore, preferably laser welding. In this regard it is noted that laser welding can take place on the interior and exterior sides of the vessel subassembly as thesecond endcap106′ has yet to be attached to theliner102.
• At the same or different time the fitting356 is attached to thefirst endcap104′ by laser welding, vibration welding, or the like. Accordingly, the fitting356 is sealingly secured to thefirst endcap104′ and theseat354 so as to prevent leakage of fluid between the fitting356, theseat354, and thefirst endcap104′. Following integrating of the fitting356 with thefirst endcap104′ andseat354, thesnap ring376 may be removed from the fitting356.
• Thesecond endcap106′, with thevalve386 extending through the encapsulatedseat354, is attached to the second end of theliner102 in the same manner as thefirst endcap322. The overwrap layer119 is helically wound around theliner102 and theendcaps104′,106′, as described hereinbefore. During use, the fitting orpipe358 is secured to the threadedportion370 of the fitting356, and fluid is pumped into the diaphragm and withdrawn from the diaphragm via the fitting356 and thepipe358. Pressurizing air is injected into thevessel300 through thevalve386.
• Although the inlet assembly described hereinbefore with reference toFIGS. 3 and 5 has been illustrated as being used in conjunction with a thermoplastic composite pressure vessel, it is considered apparent that it could be used with equal functionality in a metal pressure vessel. For example, in a metal pressure vessel having a first and second dome-shaped end, a first dome shaped end could have a metal sealing ring welded to the first metal tank dome at a location surrounding an inlet opening. Such a sealing ring would be substantially identical in function to theseat354, and would include an annular groove to receive theannular rib344 of the diaphragm and a body portion extending through the opening in the tank dome. For a metal tank assembly, the fitting356 could be integrally secured to the diaphragm adjacent to theannular rib344, such as by laser or vibration welding, but would otherwise be identical to that described hereinbefore.
• With reference toFIG. 6, athermoplastic diaphragm assembly400 according to the present invention is illustrated. Thediaphragm assembly400 includes afirst diaphragm portion402, asecond diaphragm portion404, and a fitting408. The first andsecond diaphragm portions402,404 includeopen ends402a,404athat are overlapped and secured to one another by any of the techniques described hereinbefore so as to form an overlappingjoint406. Thefirst diaphragm portion402 defines an opening through which the fitting408 sealingly extends, as illustrated. The placement and attachment of the fitting within the diaphragm assembly is described hereinafter. However, it is noted that, with thethermoplastic diaphragm assembly400 it is possible to manufacture a diaphragm subassembly that is essentially complete and adapted for placement in a pressure vessel as a unitary structure.
• Moreover, with thediaphragm assembly400 it is preferred that, since only thesecond diaphragm portion404 will be required to extend/collapse during use, thefirst diaphragm portion402 will be formed from a relatively less flexible material than that of thesecond diaphragm portion404. Forming thefirst diaphragm portion402 from a relatively stiff or non-elastic material reduces the material costs for thediaphragm assembly400.
• Thefirst diaphragm portion402 includes ascreen403 and anannular seat405. Thescreen403, which may be integrally formed with thefirst diaphragm portion402 or secured thereto, overlies the fitting408 and the port defined thereby. Thescreen403 has a series of apertures formed therein and prevents thesecond diaphragm portion404 from being pulled through the fitting408 during collapse of thesecond diaphragm portion404.
• With reference toFIG. 7, athermoplastic pressure vessel500 according to the present invention is illustrated. Insofar as several of the components of thispressure vessel500 are identical to those described hereinbefore with reference toFIG. 3, those portions are identified with identical reference numbers as used inFIG. 3, and will not be described in detail hereinafter.
• Thepressure vessel500 includes first andsecond endcaps104′,106′, aliner102, ahelical overwrap layer319, a diaphragm consisting of the second diaphragm portion404 (FIG. 6), and a fitting408. Theendcaps104′,106′ are secured to ends of theliner102, and theoverwrap layer319 is helically wrapped around the liner and endcaps. The fitting408 extends through an opening in thefirst endcap104′. The air valve is received in thesecond endcap106′, as described hereinbefore with regard toFIG. 5. Thesecond diaphragm portion404 is secured to theliner102 at a location between the first andsecond endcaps104′,106′. Naturally, the diaphragm may be like that illustrated inFIG. 6 so as to include both first andsecond diaphragm portions402,404.
• FIG. 9 illustrates attachment of the fitting408 to thefirst endcap104′ in thepressure vessel500 shown inFIG. 7.FIG. 8, to be described hereinafter, illustrates attachment of the fitting408 to thefirst endcap104′ when the diaphragm assembly is generally as shown inFIG. 6.
• With referenced toFIG. 9, the fitting408 includes radially extendingflange410, an innertubular sidewall412, and an outertubular sidewall416. Theflange410 extends from one end of the innertubular sidewall412, while the outertubular sidewall416 extends from the opposite end of the innertubular sidewall412. An annular notch or groove414 is formed in the outer surface of the innertubular sidewall412 for receipt of an optional O-ring. A steppedsurface418 is provided at the union of the inner and outertubular sidewalls412,416, and serves to assist in securing the fitting408 to theendcap104′, as will be described hereinafter.
• Thefirst endcap104′ has the ring shapedseat454 insert molded therein, as noted hereinbefore. The ring shaped seat includes anannular wall458 has an annular or radial inner surface in face to face contact with the outer surface of the fitting innertubular sidewall412 and anend face455 in abutting contact with thefitting flange410, as illustrated. Further, theendcap104′ has anupstanding wall104a′ coaxial with theannular wall458 of the ring shapedseat454. Theupstanding wall104a′ has a radially inwardly facing surface that is in face-to-face contact with the outer surface of the innertubular sidewall412. As such, the fitting408 is in substantially continuous contact with theendcap104′ and theseat454 along the length of the innertubular sidewall412 and a portion of theflange410. Accordingly, when the fitting408 is secured to theendcap104′, such as by vibration welding or other compatible techniques, a large bonding area extending from theupstanding wall104a′ of theendcap104′ to theend face455 of theannular wall458 is provided. Moreover, since the bonding or sealing surface extends outwardly over theupstanding wall104a′ and, therefore, relatively beyond theseat454, even if the bonding between theseat454 and thefirst endcap104′ fails, the vessel will still not leak due to the sealing of the fitting408 to theendcap104′ outboard of the seat.
• Moreover the steppedportion418 is useful in securing the fitting408 to theendcap104′. Since the steppedportion418 is adjacent to the annular end face of theupstanding wall104a′ of thefirst endcap104′, application of heat and pressure to the steppedportion418 will upset or stake the stepped portion, and thereby cause the steppedportion418 to flow onto and bond with the annular end face of theupstanding wall104a′. This situation is illustrated in phantom inFIG. 9 and indicated with thereference numeral418′. Accordingly, the fitting408 will be clamped on theendcap104′ by cooperation of the upset steppedportion418′ and theflange410.
• The fitting408 is formed from a thermoplastic material that is compatible with theendcap104′ and theseat454 so as to facilitate bonding or welding of the fitting thereto, preferably by vibration welding or laser welding. The fitting408 may be formed from a reinforced thermoplastic material, such as a glass reinforced thermoplastic. Preferably, the attachment or welding of the fitting408 occurs substantially continuously along the innertubular portion412, the radially inwardly facing portion of theseat454, and theannular end wall455 of theseat454, as described hereinbefore.
• FIG. 8 illustrates attachment of the fitting408 to a vessel including the diaphragm assembly illustrated inFIG. 6. Accordingly,FIG. 8 differs fromFIG. 9 in that theseat405 provided by thefirst diaphragm portion402 is secured to an inwardly facing surface of theflange410 and, thus, theflange410 is captured between theend wall455 and thediaphragm seat405. Thescreen403 is spaced a short distance from the fitting408. Accordingly, thefitting flange410 is preferably secured, by the aforementioned techniques, to the firstdiaphragm portion seat405 to form a subassembly consisting of thefirst diaphragm portion402 and the fitting408 and, optionally, thesecond diaphragm portion404. The subassembly may be installed in thefirst endcap104′ and secured thereto by welding the fitting to theend wall455 and theupstanding wall104a′, as described hereinbefore with regard toFIG. 9. It is believed that the illustrated structure has essentially been described hereinbefore, and will be readily appreciated by those skilled in the art.
• The embodiments described herein are examples of structures, systems and methods having elements corresponding to the elements of the invention recited in the claims. This written description may enable those skilled in the art to make and use embodiments having alternative elements that likewise correspond to the elements of the invention recited in the claims. The intended scope of the invention thus includes other structures, systems and methods that do not differ from the literal language of the claims, and further includes other structures, systems and methods with insubstantial differences from the literal language of the claims.

Claims (8)

1. A vessel subassembly, comprising:

a thermoplastic cylindrical liner having an inwardly facing surface and first and second ends;

a first thermoplastic endcap, said first endcap having an inwardly facing surface, an outwardly facing surface, and an open end, said outwardly facing surface of said first endcap being secured to said liner first end at said open end thereof;

a second thermoplastic endcap, said second endcap having an inwardly facing surface, an outwardly facing surface, and an open end, said outwardly facing surface of said second endcap being secured to said liner second end at said open end thereof, said liner and said first and second endcaps cooperating to define an interior volume of said vessel subassembly; and

a thermoplastic diaphragm, said diaphragm having a first side and a second side and being sealed to the inwardly facing surface of one of said first and second endcaps at the open end thereof, said diaphragm further being spaced remotely from said liner inwardly facing surface, said diaphragm defining a diaphragm interior volume that is fluidly isolated from a remainder of an interior volume of said vessel, and wherein said diaphragm is operable to expand and collapse so as to increase or decrease said diaphragm interior volume and correspondingly decrease or increase said remaining interior volume of said vessel.

2. The vessel subassembly as defined inclaim 1, further comprising an annular ring having inner and outer sides and being disposed between said diaphragm and said inwardly facing surface of said one of said first and second endcaps at the open end thereof, said diaphragm being sealed to said inner side of said ring and said inwardly facing surface of said one of said first and second endcaps being sealed to said outer side of said ring.

3. The vessel subassembly as defined inclaim 1, wherein the diaphragm is formed from a thermoplastic elastomeric material selected from the group consisting of ethyl vinyl acetate, rubber, rubber blends, and polypropylene-rubber blends.

4. A vessel subassembly, comprising:

a thermoplastic cylindrical liner having an inwardly facing surface and first and second ends;

a first thermoplastic endcap, said first endcap having an inwardly facing surface and an open end, said first endcap open end being secured to said liner first end;

a second thermoplastic endcap, said second endcap having an inwardly facing surface and an open end, said second endcap open end being secured to said liner second end, said liner and said first and second endcaps cooperating to define an interior volume of said vessel subassembly; and

a thermoplastic diaphragm, said diaphragm having a first side and a second side and being sealed directly to the inwardly facing surface of said liner at a location spaced remotely from each of said first and second endcaps so as to separate said interior volume into first and second chambers, said first chamber being defined by said first side of said diaphragm, said first endcap, and a first portion of said liner while said second chamber being defined by said second side of said diaphragm, said second endcap, and a second portion of said liner.

5. A vessel subassembly, comprising:

a thermoplastic cylindrical liner having an inwardly facing surface and first and second ends;

a first thermoplastic endcap, said first endcap being generally dome shaped and having an inwardly facing surface, an outwardly facing surface, and an open end, said first endcap outwardly facing surface being secured to said liner first end at said open end of said first endcap;

a second thermoplastic endcap, said second endcap being generally dome shaped and having an inwardly facing surface, an outwardly facing surface, and an open end, said second endcap outwardly facing surface being secured to said liner second end at said open end of said second endcap, said liner and said first and second endcaps cooperating to define an interior volume of said vessel subassembly; and

a thermoplastic diaphragm, said diaphragm having a first side and a second side and a peripheral edge, and being sealed directly to said inwardly facing surface of said first endcap at a location spaced remotely from said liner so as to separate said interior volume into first and second chambers, said first chamber being defined by said first side of said diaphragm and said first endcap inwardly facing surface while said second chamber being defined by said second side of said diaphragm, said second endcap inwardly facing surface, and said liner inwardly facing surface.

6. A vessel subassembly, comprising:

a thermoplastic cylindrical liner having an inwardly facing surface and first and second ends;

a first thermoplastic endcap, said first endcap having an inwardly facing surface and an open end, and being secured to said liner first end at said open end;

a second thermoplastic endcap, said second endcap having an inwardly facing surface and an open end, and being secured to said liner second end at said open end, said liner and said first and second endcaps cooperating to define an interior volume of said vessel subassembly; and

a thermoplastic diaphragm, said diaphragm including a first diaphragm portion and a second diaphragm portion, each of said diaphragm portions having a first side and a second side, said second diaphragm portion second side engaging the inner surface of one of said first and second endcaps in a face to face manner while said first diaphragm portion is sealed to the inwardly facing surface of one of said liner and said one of said first and second endcaps so as to separate said interior volume into first and second chambers, said first chamber being at least partially defined by said first side of said second diaphragm portion and said first side of said first diaphragm portion while said second chamber being at least partially defined by said second side of said first diaphragm portion, the inwardly facing surface of the liner, and the inwardly facing surface of the other of said first and second endcaps.

7. The vessel subassembly as defined inclaim 4, wherein said diaphragm includes a peripheral edge that is sealed to said inwardly facing surface of said liner.

8. A vessel subassembly, comprising:

a thermoplastic cylindrical liner having first and second ends;

a first thermoplastic endcap secured to said liner first end;

a second thermoplastic endcap secured to said liner second end, said liner and said first and second endcaps cooperating to define an interior volume of said vessel subassembly; and

a thermoplastic diaphragm, said diaphragm serving to separate said interior volume into first and second chambers;

wherein said diaphragm includes a first diaphragm portion, a second diaphragm portion, and a ring, said first diaphragm portion and said second diaphragm portion being secured to one of said first and second endcaps, said ring being interposed between a peripheral edge of said first diaphragm portion and said inner surface of said one of said first and second endcaps, said ring being sealed to each of said first diaphragm portion peripheral edge and said inner surface of said one of said first and second endcaps, wherein said second diaphragm portion covers said inner surface of said one of said first and second endcaps and wherein said first diaphragm portion extends from said second diaphragm portion toward the other of said first and second endcaps.

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