Abstract:
The invention relates to a composite pressurized gas tank including a sealed inner casing ( 12 ), comprising an opening ( 18 ) on one of the ends of the casing, and a base ( 13 ) attached to the opening ( 18 ) of the inner casing ( 12 ), the base ( 13 ) being provided so as to receive or have built therein a valve or faucet, the tank also including an outer mechanical reinforcement casing ( 11 ) that is placed on at least a portion of the inner casing ( 12 ). Said tank is characterized in that at least a portion of the gap ( 14 ), located between the inner casing ( 12 ) and the outer mechanical reinforcement casing ( 11 ), is connected to at least one area ( 15 ) for collecting the gas capable of accumulating in said gap ( 14 ). The at least one collecting area ( 15, 137 ) leads into a predetermined discharge area ( 16, 26, 23 ) that is located outside the gap ( 14 ).

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a 371 of International PCT Application PCT/FR2011/050170, filed Jan. 28, 2011, which claims priority to FR Application 1050984, filed Feb. 11, 2010, the entire contents of which are incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    The present invention relates to a composite tank, as well as an assembly comprising a member for receiving and/or dispensing gas and such a tank. 
         [0003]    The invention relates more particularly to a composite pressurized gas tank comprising a sealed internal casing having an opening at one of its ends, a base fixed in the region of the opening of the internal casing, the base being provided to receive or incorporate a valve or faucet, the tank also comprising an external mechanical reinforcement casing arranged on at least one part of the internal casing. 
         [0004]    Applications which require the storage of gas use the technology of composite materials to provide an excellent compromise between the mass of the outer packaging and the mass of the stored gas. For example, so-called “type IV” tanks or bottles of gas made of composite materials comprise:
       a sealed internal casing (also called a “liner”) consisting, for example, of plastics and generally a polymer material such as polyamide, the function thereof being to provide the seal of the outer packaging relative to the type of gas stored,   an external mechanical reinforcement casing (generally made of carbon fibers immersed in epoxy-type resin). Said external casing or layer does not have to be sealed but current manufacturing processes do not allow this to be perfectly controlled. As a result, said external casing which is generally obtained by winding, may be sealed uniformly or locally,   a (generally metal) base, the function thereof being to permit the connection of the bottle to a valve or faucet (either with or without integrated pressure relief) providing the fluidic connection with the consumer application point for the gas of the tank.       
 
         [0008]    Reference may be made, for example, to FR2744517A1 or EP2000734A2 or US2007012551A1 or US2009071930A1. 
         [0009]    Even if said tanks are designed as sealed, during a specific period of storage a certain quantity of gas is liable to pass through the internal casing to the outside. In particular, when the gas contains small molecules, such as for example helium or hydrogen, and the storage pressure is raised (for example from 450 bar to 800 bar) a certain quantity of gas passes through the internal casing. Said gas is trapped in the gap located between the internal casing and the external mechanical reinforcement casing. 
         [0010]    The pressure at which said gas is trapped in the gap in certain cases may be equal to the storage pressure in the internal casing (said pressure of the trapped gas depends on various parameters, including the difference in the permeation flow between the internal casing and the external mechanical reinforcement casing). 
         [0011]    The time required for emptying a tank is generally much less than the time required for reverse permeation (return) of the quantity of trapped gas from the gap toward the interior of the tank. As a result, when emptying the tank, a difference in pressure may be created between the gap and the interior of the tank. Said difference in pressure mechanically stresses the sealed internal casing toward the interior of the tank. Said sealed internal casing is not designed to resist said stresses and blistering may thus be formed in the interior of the tank. The volume of said blistering permits the pressure of the trapped gas to be reduced until it finds a mechanical equilibrium. The successive filling and emptying of the tank may lead to the occurrence of fatigue and premature wear of the sealed internal casing on the periphery of the blistering of the bottle (for example folds forming fissures). This reduces the life of the tank and, should this happen, may cause dangerous leaks. 
         [0012]    An object of the present invention is to remedy all or some of the drawbacks of the prior art set forth above. 
       SUMMARY 
       [0013]    To this end, the tank according to the invention and according to the generic definition provided by the preamble above, is essentially characterized in that at least one part of the gap located between the internal casing and the external mechanical reinforcement casing is connected to at least one collecting zone for the gas which is capable of accumulating in said gap, the at least one collecting zone opening into a specific evacuation zone outside the gap. 
         [0014]    The invention also makes it possible to resolve or alleviate said problem of blistering by avoiding gas being trapped between the fiber reinforcement and the sealed internal casing. 
         [0015]    The invention is able to permit the drainage or even the controlled collection of gas as a result of permeation from the sealed internal casing. 
         [0016]    Moreover, embodiments of the invention may comprise one or more of the following features:
       the evacuation zone comprises the atmosphere,   the evacuation zone comprises the internal volume of the internal casing, the at least one collecting zone opening into the internal volume of the internal casing via a pressure-sensitive flap valve and permitting the passage of gas toward the internal volume of the internal casing solely in the event of a specific difference in pressure between the at least one collecting zone and the internal volume of the internal casing,   the evacuation zone comprises at least one conduit and/or cavity delimited by the base,   the base comprises an upper part of generally tubular shape and a lower portion, one part of the surface of the internal casing being in sealed contact with at least one part of a surface of the lower portion of the base,   at least one collecting zone is formed in the region of the external surface of the portion of the internal casing which is located in the region of the base;   at least one collecting zone is formed in the region of an external surface of the base,   the at least one collecting zone comprises at least one groove forming at least one collecting and circulation channel for the gas,   the collecting zone communicates with at least one volume located inside the body of the base and provided to receive a valve or a faucet,   the tank comprises a faucet, with or without a pressure relief member, arranged in a sealed manner in the base,   the evacuation zone comprises at least one volume located between the body of the base and the body of the faucet arranged in the base, said volume being in fluidic communication with the collecting zone,   the evacuation zone comprises a volume or a channel inside the body of the faucet,   the evacuation zone comprises an internal evacuation circuit in the body of the faucet, the internal evacuation circuit being in fluidic communication with the collecting zone,   the faucet comprises an internal extraction circuit and/or an internal filling circuit in fluidic communication with the internal volume of the internal casing, the internal evacuation circuit of the faucet being at least partially separate from the extraction circuit and/or the filling circuit,   the tank is a tank of the IV type,   the assembly between the internal casing and the base is sealed,   the internal casing consists of polymer such as polyimide,   the base comprises or consists of at least one of the following materials: a metal material, an aluminum alloy (for example 7000 series), steel, for example of the 350D4 type, stainless steel, for example of the AISI 316L type, etc.),   the mechanical reinforcement layer comprises a resin, for example of the epoxy type, and fibers such as carbon fibers,   at least one part of the groove(s) is(are) longitudinal, i.e. oriented in a direction parallel or substantially parallel to the longitudinal axis of the tank,   the volume located between the body of the base and the body of the faucet and forming at least one part of the evacuation zone is delimited by at least one seal isolating said volume from the interior of the internal casing,   the volume located between the body of the base and the body of the faucet and forming at least one part of the evacuation zone is delimited by at least one seal isolating said volume from the ambient air outside the faucet,   a layer of drainage material is arranged at least locally between the internal casing and the reinforcing layer to delimit a gap of specific thickness,   the layer of drainage material comprises at least one of the following: a polyurethane foam, non-impregnated mineral and/or synthetic fibers,   one end of the internal casing is sandwiched in the thickness of the base.       
 
         [0041]    The invention also relates to an assembly for delivering gas comprising a tank according to any one of the features above or below and a member for receiving and/or dispensing gas, comprising an end for selective connection to the faucet to provide a transfer of gas to or from the tank via the faucet in which the member comprises a circuit for recovering gas which communicates selectively with the evacuation zone when the member is connected to the faucet. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0042]    The invention may also relate to any device or alternative method having any combination of the features above or below. 
           [0043]    Further particularities and advantages will appear from reading the following description, made with reference to the figures, in which: 
           [0044]      FIG. 1  shows a view in longitudinal section of a first embodiment of a tank according to the invention provided with a faucet, 
           [0045]      FIG. 2  shows a view in section of a detail of the upper part of the tank of  FIG. 1  in which a member for receiving gas is connected to the faucet of the tank, 
           [0046]      FIGS. 3 to 5  show in schematic and simplified form the structure and operation of, respectively, three embodiments according to the invention of the assembly comprising a tank, a faucet, and a receiving member, 
           [0047]      FIG. 6  shows a sectional view of a detail of a second embodiment according to the invention of a tank provided with a faucet and connected to a receiving member, 
           [0048]      FIG. 7  shows a sectional view of a detail of a third embodiment according to the invention of a tank provided with a faucet which is connected to a receiving member, 
           [0049]      FIG. 8  shows a sectional view of a detail of a fourth embodiment according to the invention of a tank provided with a faucet connected to a receiving member. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0050]      FIG. 1  illustrates a composite pressurized gas tank  1 . Preferably, the tank (which may also be denoted by the term “bottle”) is a composite tank of the IV type. 
         [0051]    The tank  1  comprises a sealed internal casing  12  (also called a “liner”) having an opening  18  at one of its ends. The sealed internal casing  12  has, for example, an oblong shape. The opening  18  is, for example, circular. 
         [0052]    A base  13 , for example made of metal, is fixed in the region of the opening  18  of the internal casing  12 . The base  13  is conventionally provided to receive or incorporate a valve or a faucet. An external mechanical reinforcement casing  11  is, moreover, arranged on at least one part of the external surface of the internal casing  12  (and preferably over its entire surface). For example, the external mechanical reinforcement casing  11  comprises fibers and a resin. The thickness of the external mechanical reinforcement casing  11  may be adapted according to the storage pressure of the gas. In the present text, the external casing  11  may also be denoted “external layer” or “reinforcement layer”. 
         [0053]    A “simple” faucet  2  or a faucet with integrated pressure relief is removably mounted in the base (naturally it is possible to conceive that the faucet  2  is formed integrally with the base  13 ). For reasons of simplification of the figures, the faucet  2  is shown partially and in simplified form. 
         [0054]    A sealed contact is made between the internal surface  121  of the internal casing  12  and the external surface  131  of the base  13 . Said sealed contact may be implemented, for example, via a connecting element  17  such as adhesive, a seal, or any other appropriate means. 
         [0055]    As shown, the external reinforcement layer  11  may extend and cover the lower part  132  of the base  13  (which is preferably flared). 
         [0056]    The resin of the external casing  11  is wetted and bonded to the metal base  13 . The corresponding connection between the external mechanical reinforcement casing  11  and the metal base  13  is thus sealed. 
         [0057]    The gap  14  located between the external mechanical reinforcement casing  11  and the internal casing  12  is capable of trapping the gas as a result of permeation from the internal casing  12 . 
         [0058]    According to one advantageous particularity of the invention, at least one part of the gap  14  communicates directly or indirectly with at least one collecting zone  15  for gas capable of accumulating in said gap  14 . Moreover, the at least one collecting zone  15  opens into a specific evacuation zone  16 ,  26 ,  23  outside the gap  14  (a secure zone). 
         [0059]    The collecting zone  15  and the evacuation zone  16 ,  26 ,  23  may be dimensioned according to the maximum expected permeation flow for the sealed internal casing  12 . Said permeation flow is a function of, in particular:
       the nature and the pressure of the stored gas,   the material forming the internal casing  12  and its surface in contact with the gas.       
 
         [0062]    Said collection and said evacuation of gas make it possible to avoid premature wear of the tank. The quantity of gas collected may also be measured in order to evaluate the state of the internal casing. 
         [0063]    For example, the collecting zone comprises grooves  15 . In the example of  FIG. 1 , the gap  14  opens into the grooves  15 , which are for example longitudinal, formed on the external surface of the internal casing  12 . 
         [0064]    Collecting grooves  15  may, in particular, be located in the region of the zone of the internal casing  12  which is confined (fixed) between the base  13  and the reinforcing layer  11 . 
         [0065]    Said grooves  15 , which communicate with the gap  14 , thus make it possible to convey the gas trapped in the gap  14  to an external evacuation zone. The evacuation zone may, for example, simply be the outside (ambient atmosphere around the tank). When the gas is inflammable or dangerous, the evacuation zone preferably recovers the gas in a more secure manner. For example, as shown in  FIGS. 1 and 2 , the collecting grooves  15  may open into an annular cavity  19  located at the end of the circular opening  18  of the casing  12 . 
         [0066]    The annular cavity  19  is, for example, connected to one or preferably several orifices or conduits  16  formed in the base  13 . 
         [0067]    The orifices  16  may open into and communicate in the central zone of the base  13  where a faucet  2  is fixed. For example, the faucet  2  is fixed in the base by screwing, by means of a system comprising a thread  27  and a tapped portion. 
         [0068]    The orifices  16  converge, for example, toward a chamber  26  located between the metal base  13  and the faucet  2 . The chamber  26  has, for example, an annular shape. The chamber  26  may be delimited in a sealed manner in the lower part by a first seal  25  which isolates the fluid stored inside the tank. The first seal  25  is, for example, interposed between the base  13  and the faucet  2  (for example in a groove). 
         [0069]    In the upper part, the chamber  26  may be isolated from the outside ambient air by a second seal  24 . The second seal  24  is, for example, interposed between the base  13  and the faucet  2 . 
         [0070]    As shown, the faucet  2  preferably has at least one bore  23  in fluidic communication with the chamber  26 , to evacuate the gas from the gap  14 . Preferably, without limiting the invention, the bore(s)  23  forms(form) a circuit for the gas which is separate from the extraction circuit  22  of the faucet  2  by means of which the gas is withdrawn from the tank  1 . 
         [0071]    Preferably, the circuit formed by the bore(s)  13  comprises an end provided to be in fluidic connection with an evacuation circuit formed in the member  3  for receiving and/or dispensing gas which is connected to the faucet  2 . In other words, by being connected to the faucet  2 , the member  3  for using gas from the tank or the member  3  providing the filling of the tank preferably recovers the gas from the gap  14 . 
         [0072]    In other words, the base  13  makes it possible to channel the gas from the gap  14  toward the connection of the tank, the gas then being evacuated, via the faucet  2 , by a receiving member  3 . 
         [0073]    The structure is shown schematically in  FIG. 3 . The extraction circuit  22  of the faucet  2  makes it possible to extract gas from the tank  1  toward the member  3 . The extraction circuit  22  comprises, for example, a flap valve  222  and possibly a filter  221 . The circuit  23  makes it possible to evacuate the gas from the gap parallel to the extraction circuit  22 . In addition to the emptying of the tank, the circuit  22  may, if required, be also provided to ensure the filling of the tank. 
         [0074]    Said embodiment of the faucet  2  makes it possible to facilitate the recovery of gas as a result of permeation from the internal casing  12  by means of a dedicated circuit  23 . As shown in  FIG. 2 , the member  3  is preferably connected to the faucet  2  via a rapid connection interface  29 . In this manner, the faucet  2  makes it possible for the emptying  22  and evacuation  23  circuits to be connected in a sealed manner to the respective circuits of the receiving member  3  which, for example, forms part of the consumer application of the gas of the tank. 
         [0075]    When the tank  1  is connected to the gas consumer application point, the coaxial rapid connection interface  29  is connected to the receiving member  3 . The connection between the member  3  and the faucet  2  comprises, for example, a system with locking elements  291  (for example locking pins) which are mechanically fastened in housings  31  (for example bayonet fittings) so as to prevent the translation of the rapid connection  29  of the faucet  2  relative to the receiving member  3 . 
         [0076]    The faucet  2  has one end of specific shape provided to be accommodated in a housing adjoined to the member  3 . 
         [0077]    For example, a first cylindrical portion  292  of the faucet  2  is centered in a bore  32  adjoined to the member  3 . A seal  33  carried by the member  3  provides the sealing function and isolates the evacuation circuit E of the gas from the gap  14  relative to the external ambient air. 
         [0078]    A second cylindrical portion  293  of the end of the faucet  2  is centered in a second corresponding bore  34  of the member  3 . A second seal  35  provides the isolation of the extraction circuit  22  and the evacuation circuit E. 
         [0079]    In the connected position, the annular volume located about the second cylindrical portion  293  (and defined between the two seals  33 ,  35  of the member  3 ) makes it possible to connect the evacuation circuit  23  of the faucet  2  to an orifice E formed in the receiving member  3 . Said orifice provides, therefore, the evacuation of gas as a result of permeation from the internal casing  12 . Said permeation gas may thus be controlled in the region of the consumer application point (member  3 ). For example, said permeation gas is evacuated to the atmosphere in a secure zone or recycled in the consumer application point. The flow rate of said evacuated gas may also be measured. 
         [0080]    The extraction channel  22  passes through the body  21  of the faucet  2  and connects the interior of the tank to the end  294  of the coaxial rapid connection interface  29  of the member  3 . When the faucet  2  of the tank  1  is connected to the gas consumer application (member  3 ), the extraction circuit opens into the circuit V of the receiving member  3  provided for the receiver. 
         [0081]    In the variant of  FIG. 4 , a pressure relief member  223  lowering the pressure to a specific value may be incorporated in the extraction circuit  22  upstream of the isolating valve  222  (i.e. on the tank side). As shown, the filling circuit  224  of the faucet  2  may comprise a dedicated filling connector  225  to fill the tank  1 . The filling circuit  224  may be separate from the extraction circuit  22  or may comprise a common portion. 
         [0082]    As shown in  FIG. 5 , the pressure relief member  223  may be placed downstream of the isolating member  222  (i.e. on the member side). As above, preferably, a filling circuit  224  with a dedicated connector  225  is provided to fill the tank. 
         [0083]      FIG. 6  shows a variant which is distinguished from that of  FIG. 2  in that a drainage material  151  is arranged between the internal casing  12  and the external mechanical reinforcement casing  11 , so as in particular to maintain a minimum spacing, making it possible to ensure the evacuation flow. 
         [0084]    For reasons of concision, elements which are identical to those described above are denoted by the same reference numerals and are not described again. 
         [0085]    Said layer of drainage material  151  comprises, for example, a polyurethane foam and/or non-impregnated mineral and/or synthetic fibers or the like. 
         [0086]    The drainage material  151  is provided to promote the circulation of the permeation gas trapped in the gap  14  toward the collecting zone  15 , then to the evacuation zone (orifices  16  of the base  13 , then circuits  23 , E, etc.). 
         [0087]      FIG. 7  illustrates a further variant in which the base  13  comprises two parts: a first internal part  132  and a second external part  131 . The internal casing  12  of the tank is sandwiched in a sealed manner between said two parts of the base  13  (said configuration has the advantage of permitting the use of adhesive to be avoided). 
         [0088]    The internal part  132  of the base  13  may, for example, comprise a thread  133  to which a tapped portion of the external part  131  is screwed. 
         [0089]    The external part  131  of the base  13  may comprise one or more collecting grooves  137  for gas trapped in the gap  14 . Said grooves  137  direct the gas to the evacuation orifices or conduits  16 . 
         [0090]    As before, the evacuation conduits  16  may converge toward a chamber  26  (for example an annular chamber). Said chamber  26  communicates with a groove  134  formed in the base  13 . For example, the groove  134  is formed in the threaded portion  133  and conducts the gas to a second chamber  136  (for example an annular chamber) formed between the base  13  and the body  21  of the faucet  2 . Said second chamber  136  is connected to the evacuation circuit  23  formed in the faucet  2 . 
         [0091]    The variant of  FIG. 8  is distinguished from that of  FIG. 7  in that a layer of drainage material  151  is arranged between the internal casing  12  and the external mechanical reinforcement casing  11 . The layer of drainage material  151  (which comprises for example polyurethane foam, non-impregnated mineral or synthetic fibers, etc.) is provided to maintain a minimum spacing in the region of the gap  14 , permitting the specific evacuation flow to be ensured. 
         [0092]    Thus, it is conceived that the invention, whilst being of simple and inexpensive structure, makes it possible to avoid the undesirable effects of permeation of the composite gas tanks. The invention relates in a particularly advantageous manner to composite tanks of the IV type, for the storage of a gas composed of or comprising hydrogen (at a pressure ranging between 450 and 800 bar, in particular). 
         [0093]    It will be understood that many additional changes in the details, materials, steps and arrangement of parts, which have been herein described in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Thus, the present invention is not intended to be limited to the specific embodiments in the examples given above.