Abstract:
A pressure vessel with a protective jacket disposed thereon, wherein the vessel is formed of a metal liner surrounded by a layer of thermoplastic composite filament winding and a protective jacket disposed thereon that facilitates stacking and portability of the vessel, while also providing sufficiently sized openings for visual inspection of the composite layer integrity.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority from U.S. Provisional patent application Ser. No. 60/564,776, filed Apr. 23, 2004. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The subject invention is directed to pressure vessels, and more particularly to a hybrid pressure vessel formed of an inner liner and outer composite layer with a protective jacket disposed thereon. 
     2. Background of the Related Art 
     Pressure vessels come in all sizes and shapes, and are made from a variety of materials. The need for light weight pressure vessels has existed and still exists as there have been many attempts to make light weight pressure vessels that are able to store fluids under high pressures for long periods of time, maintain structural integrity, sustain repeated pressurization and depressurization, be substantially impermeable and corrosive free and easy to manufacture, among other things. 
     Increased use of alternative fuels to fuel vehicles, such as compressed natural gas and hydrogen, and the requirement for ever greater fuel range, has created a need for lightweight, safe tanks with even greater capacity and strength. Increasing the capacity and strength of a pressure vessel can be achieved by increasing the amount or thickness of materials used for structural support. However, this can result in a significant increase in the size and/or weight of the vessel, which, among other things, typically increases the cost of the tank due to increased material costs and the costs associated with transporting the heavier vessels. 
     Clearly, there is a need in the art for a lightweight pressure vessel that is impermeable, corrosive free and can handle the increasing capacity and pressure demands. Furthermore, there is a need for a method of forming this pressure vessel so it can be sold at a competitive price. 
     SUMMARY OF THE INVENTION 
     The subject invention is directed to a unique pressure vessel, which satisfies the aforementioned needs in the art, among other things. In accordance with the subject invention, the thickness of the liner and outer layer are minimized to reduce the cost associated with vessel production without compromising the vessel strength or making the vessel unsuitable for its intended use, particularly with respect to any applicable regulatory standards, such as those promulgated by the Department of Transportation. Thus, the liner and outer layer of the present invention are advantageously optimized by, among other things, a planning process that includes balancing material and production cost versus vessel integrity. 
     In particular, the present invention provides a pressure vessel with protective jacket that includes a vessel formed by an inner tank defining an upper end portion and a lower end portion, and an outer reinforcing layer disposed on the inner tank. The outer reinforcing layer is fabricated of a thermoplastic material, preferably polypropylene, commingled with glass fibers. A protective jacket configured and dimensioned to engage the vessel is disposed thereon. The protective jacket includes an upper support rim, a lower support rim and a plurality of longitudinal ribs connecting the upper support rim and lower support rim, and a handle protruding from the upper support rim. The protective jacket may be separable into at least two sections. 
     Preferably, the inner tank is formed of a material having a higher modulus of elasticity and a lower elastic strain limit than the material used to form the outer reinforcing layer. 
     Preferably, the lower support rim includes a bottom portion disposed over the lower end portion of the vessel, which preferably further includes an inner shoulder. The protruding handle can include a support structure for forming a non-permanent engagement with the bottom portion of the lower support rim. 
     The present invention is also directed to a method of manufacturing a pressure vessel with protective jacket comprising the steps of securing a first endcap and a second endcap to an inner liner to form a tank, heating glass filaments, commingling the filaments with a thermoplastic material, winding the thermoplastic material and commingled filaments onto the tank while heating to form a vessel, and attaching a protective jacket to the vessel, where the protective jacket includes an upper support rim, a lower support rim and a plurality of longitudinal ribs connecting the upper support rim and lower support rim, and a handle protruding from the upper support rim. 
     These and other aspects of the pressure vessel of the subject invention will become more readily apparent to those having ordinary skill in the art from the following detailed description of the invention taken in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that those having ordinary skill in the art to which the present invention pertains will more readily understand how to make and use the pressure vessel with protective jacket of the present invention, embodiments thereof will be described in detail hereinbelow with reference to the drawings, wherein: 
         FIG. 1  is a perspective view of a pressure vessel with protective jacket constructed in accordance with a preferred embodiment of the subject invention; 
         FIG. 2  is a partial cross section view of the pressure vessel with protective jacket shown in  FIG. 1 ; 
         FIG. 3  is another partial cross-section view of the pressure vessel with protective jacket shown in  FIG. 1 , illustrating the separable sections of the jacket; 
         FIG. 4  is a top view of the pressure vessel with protective jacket shown in  FIG. 1 ; 
         FIG. 5  is a partial cross-section view taken of more than one pressure vessel with protective jackets shown in  FIG. 1  stacked together; 
         FIG. 6  is a schematic view of an exemplary process for forming a pressure vessel with protective jacket in accordance with the present invention; 
         FIG. 7  is a front view of a tank constructed in accordance with the present invention prior to the outer layer being disposed thereon; and 
         FIG. 8  is a front view of the tank shown in  FIG. 7  after the outer layer has been applied thereon. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring now to the drawings wherein like reference numerals identify similar aspects and/or features of the subject invention there is illustrated in  FIGS. 1-5  a pressure vessel  10  configured in accordance with a preferred embodiment of the subject invention and designated generally by reference numeral  10 . A pressure vessel constructed in accordance with the present invention is suitable applications including, but not limited to, storing propane, refrigerant gas, and liquids or gases at low or high pressure. 
     Pressure vessel  10  includes a generally cylindrical inner liner  12 , first and second dome-shaped, semi-hemispherical endcaps  14  and  16 , respectively. Endcaps  14  and  16  may be of any size or shape, such as frustro-conical or flattened, and may be identical or different. First and second endcaps  14  and  16  are secured to first and second end rims  18  and  20  of inner liner  12 , respectively, which may be accomplished by any conventional welding techniques known in the art, such as laser welding. Liner  12  and first and second endcaps  14  and  16  cooperate to define defining a vessel storage cavity  22 . 
     In this embodiment, first endcap  14  includes a central aperture  24  defined therein for receiving a valve boss  26 , which is secured to aperture  24  by any conventional welding techniques known in the art. Valve boss  26  is configured to receive a valve fitting assembly  28  therein, and together permits the ingress or egress of fluids to cavity  22 . 
     Preferably, liner  12 , first and second endcaps  14  and  16 , and valve boss  26  (collectively referred to herein after as the “tank”) are constructed of an inert, impermeable and non-corrosive material having a high modulus of elasticity, generally 10 million psi or greater, and a low elastic strain generally ranging from about 0.05% to about 1%. The tank and valve assembly  28  are preferably made of steel, but may also be fabricated of metals such as, but not limited to, aluminum, steel, nickel, titanium, platinum, or any other material which would provide suitable structural support in accordance with the present invention. 
     A reinforcing layer  30  fabricated of one or more layers of a material having a higher elastic strain limit than that of the material used for the tank is disposed over the tank. Layer  30  can consist of a composite that includes a skeleton that imparts desireable mechanical properties to the composite, such as a high tensile strength, and a matrix of material having high ductility that can bind the composite to render it stiff and rigid, among other things. Layer  30  reinforces and provides impact resistance to vessel  10 . 
     Preferably, the composite material in layer  30  consists of fibers or filaments which are commingled or impregnated with a thermoplastic resin. The impregnated filaments may consist of, but are not limited to, combinations of glass, metal, aramid, carbon, graphite, boron, synthetics, resins, epoxies, polyamides, polyoelfins, silicones, and polyurethanes, among other things. Preferably, the filaments are a composite of thermoplastic resin, such a vinyl epoxy or polypropylene, and glass fiber. The filaments can be formed from a commingled thermoplastic and glass fiber fabric sold as TWINTEX, commercially available from Saint-Gobain Vetrotex America Inc. The outer surface of layer  30  may include an additional layer of gel coating (not shown) or other finishing coatings. Preferably, the composite material used in layer  30  is a recyclable material. 
     An exemplary method of making vessel  10  in accordance with the present invention is shown in  FIG. 6 . In this embodiment, glass filaments  32  are drawn from a supply  34  onto tension controlling rollers  36  and heated in oven  38  before being impregnated or commingled with a thermoplastic material, such as polypropylene, supplied by an extruder  39 . Filaments  32  are preferably heated to a temperature sufficient to melt the thermoplastic resin, which assists the impregnation process. The tank is supported on a mandrel  40  which preferably rotates the tank while the impregnated filaments are wrapped continuously thereon using a hot wind technique in which the internal layers are heated by heating element  42 . Preferably, heating element  42  heats the filaments to a temperature sufficient to melt the impregnated thermoplastic material, which becomes sticky and assists in adhering each layer applied onto the tank. Upon cooling, the thermoplastic impregnated filaments wrapped about the tank consolidate to form layer  30 . A gel coating may be applied to layer  30 . Valve fitting assembly  28  is secured to valve boss  26  to form vessel  10 . 
     In accordance with the present invention, the advantages of the materials selected for liner  12 , endcaps  14  and  16  and layer  30  are optimized in that the materials used to construct vessel  10  and amount or thickness thereof are advantageously selected based on achieving a desired structural integrity (e.g., capable of withstanding repeated pressurizations and depressurizations at pressures ranging from about 0 psi to about 10,000 psi without leaking fluid stored therein), while also minimizing the expense and weight of vessel  10 .  FIG. 7  illustrates liner  12 , with endcaps  14  and  16  secured thereto without outer layer  30  disposed thereon and  FIG. 8  illustrates vessel  10  after application of outer layer  30  in an exemplary configuration. 
     In the preferred embodiment, a protective jacket  44  having an upper support rim  46  disposed substantially about the periphery of an upper portion  48  of the tank and a lower support rim  50  disposed substantially about the periphery of a lower portion  52  of the tank to form vessel  10 . Upper and lower support rims  46  and  50  are preferably configured to fit onto the tank to restrict movement of the tank within the confines of protective jacket  44 . Protective jacket  44  is preferably constructed of a rigid, lightweight material, such as a hard plastic. 
     Upper support rim  46  is connected with lower support rim  50  by a plurality of longitudinal ribs  56  disposed substantially adjacent a middle portion  54  of vessel  10 . Preferably, and as shown in this embodiment, longitudinal ribs  56  are of thickness and spaced apart in a configuration to provide gaps  57  that permit visual inspection of reinforcement layer  30 . 
     Upper support rim  46  includes a handle  58  configured to permit access to valve fitting assembly  28 . Preferably, handle  58  is ergonomically designed to assist transport of vessel  10 . In the embodiment shown herein, handle  58  includes substantially symmetrical protruding support arms  60   a,b  and  62   a,b . Support arms  60   a,b  are connected at distal ends thereof by gripping bar  64   a , and support arms  62   a,b  are connected at distal ends thereof by gripping bar  64   b , respectively. 
     Preferably, protective jacket  44  is configured to separate longitudinally into half sections  44   a  and  44   b.  Half sections  44   a  and  44   b  may be held together by any conventional engagement, such as snap-fitting portions, or other corresponding non-permanent connections, and disengaged accordingly. 
     Preferably, handle  58  is configured to form a non-permanent engagement with lower support rim  50  to facilitate transporting and stacking a plurality of vessels  10 . In this embodiment, gripping bars  64   a  and  64   b  are curved and configured to fit about the outer periphery of an inner shoulder  66  defined on lower support rim  50  to form an engagement. 
     Although the pressure vessel of the subject invention has been described with respect to a preferred embodiment, those skilled in the art will readily appreciate that changes and modifications may be made thereto without departing from the spirit and scope of the subject invention as defined by the appended claims.