Abstract:
There is provided a safety valve to release excess pressure from a portable gas container for the prevention of an explosion, wherein, when the internal pressure of a portable butane gas container increases over certain level, the safety valve instantaneously operates to release the excess pressure gas from the container at once through an excess pressure gas outlet, thereby sufficiently lowering the pressure inside the container to prevent the container from exploding.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Korean Patent Application No. 2013-0127536, filed Oct. 25, 2013, the disclosure of which is hereby incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a safety valve of a portable gas container and more particularly, to a safety valve to release the excess pressure from a portable gas container for the prevention of an explosion, wherein, when the internal pressure of a portable butane gas container increases over certain level, the safety valve instantaneously operates to release the excess pressure gas from the container at once through an excess pressure gas outlet, thereby sufficiently lowering the pressure inside the container to prevent the explosion of the container. 
     2. Description of the Related Art 
     In general, portable gas containers include a portable butane gas container charged with a butane mixture having a butane gas among liquid petroleum gases as a main ingredient, which is used for a portable gas range, and aerosol containers, such as hair spray, insecticide, lacquer spray, etc., which use a liquid petroleum gas, etc. as a propellant. These portable gas containers discharge the contents to the outside by using the gas pressure within the containers. When these containers are charged with the contents, the pressure over certain level always exists in the containers. 
     When a butane gas container receives high heat during the distribution process or upon use, the pressure of the liquid gas contained in the butane gas container increases to explode the container. Especially, in the butane gas container used for a portable gas range, when a user uses it without following the safety regulations or when high temperature or pressure over certain level is applied to it, the internal pressure increases so that the container may deform or explode. Therefore, the pressure which the portable gas container endures, deforms and bursts is defined by law. 
     Technology exists for a safety valve to release an excess pressure gas of a portable gas container, thereby operating to prevent the explosion of the container when the pressure within the container reaches over certain level, Korean Patent Registration No. 431590 relates to an “apparatus for preventing the explosion of a portable gas range” and Korean Patent Registration No. 515120 relates to a “safety apparatus for excess pressure in a gas fuel container”. However, these have some realistic problems in that assembly work is difficult and they do not properly operate at set pressure. Therefore, the applicant/inventor of the present invention has conducted much research and development to solve the problems of the prior art. As a result, the applicant/inventor obtained the following patents: Korean Patent Registration No. 914620 for a “safety valve for a portable gas container”, Korean Patent Registration No. 1064633 for a “safety valve for a portable gas container”, Korean Patent Registration No. 1281536 for a “safety valve for a portable gas container, functioning to prevent excess pressure”, and Korean Patent Registration No. 1292010 for a “safety valve for a portable gas container”. The applicant/inventor still continues the relevant research and development at great time and expense. In addition to the foregoing, the applicant/inventor has developed and commercialized some technology to prevent the explosion of a portable butane gas container. 
     However, many butane gas containers with the safety valves as produced and distributed have the problem in that the safety valves fail to be opened at once to instantaneously release the excess pressure gas at once when the gas pressure in the container reaches to certain level. Furthermore, since a little bit of gas may leak between the mounting cup and the gasket, it causes a problem such as fire, etc. 
     SUMMARY OF THE INVENTION 
     Therefore, it is an object of the present invention to provide a safety valve to release any excess pressure from a portable gas container for the prevention of an explosion, wherein a valve stem housing to be installed in a mounting cup of a portable butane gas container is integrally formed with a safety valve housing and the safety valve housing is formed in a multiple cylinder shape. When the internal pressure of the gas container increases over a certain level, the safety valve installed in the safety valve housing instantaneously opens to release any excess pressure gas of the container at once to the outside through an excess pressure gas outlet formed at the mounting cup, thereby sufficiently lowering the internal pressure of the container to prevent the explosion of the gas container. 
     In accordance with an embodiment of the present invention, there is provided a safety vale to release excess pressure from a portable gas container for the prevention of an explosion, comprising: a safety valve housing with first and second diameter portions integrally formed in a cylindrical shape, the first and second diameter portions being different from each other in diameter; a shaft with a body, a top projection formed on a top of the body, a gas outflow portion and a gasket locking portion formed at a lower part of the body, the shaft positioned inside the safety valve housing; a stopper with a lower part being open, an upper part being closed except for a center where a through-hole is vertically formed, and a side wall vertically formed along the edge of the upper part to provide a space where the gas releases, wherein the stopper is positioned so that the through-hole receives the top projection and the outer circumferential surface of the side wall is secured to the inner circumferential surface of the first diameter portion of the safety valve housing; a spring fitted around the body of the shaft and positioned between the gas outflow portion of the shaft and the stopper; and a first gasket positioned between the first diameter portion of the safety valve housing and an excess pressure gas outlet  13  of the mounting cup; and a second gasket positioned to be received around the gasket locking portion  323  formed at the lower part of the shaft, so that an upper part of the second gasket is secured to a lower part of the gas outflow portion. 
     Preferably, the second gasket further comprises: a top side being open, a body with a bottom side being closed and a side wall being formed upwardly in a cylindrical shape, along the edge of the bottom side, and a protruding portion of the upper part of the second gasket having a circular cross section being formed at an upper end of the side wall. 
     Preferably, the first diameter portion of the safety valve housing has a greater diameter than the second diameter portion and the first and second diameter portions are formed with a slope therebetween. When the pressure of the gas charged in the gas container is normal, the bottom side of the second gasket is positioned to seal an opening formed on a lower part of the second diameter portion of the safety valve housing and when the second gasket is forced to move upwardly, to the maximum, by the excess pressure gas in the gas container, the protruding portion of the second gasket moves from the upper part of the second diameter portion. 
     Preferably, the shaft and the stopper further comprise: vertically penetrating grooves formed at the equidistant intervals on the gas outflow portion of the shaft and the side wall of the stopper, respectively, to release the excess pressure gas. 
     Preferably, the second gasket comprises: separable structures of a first unit and a second unit. When the pressure of the gas in the container is normal, the first unit in an O-ring shape is positioned between the gas outflow portion and the gasket locking portion of the shaft so that its outer circumferential surface is secured to the inner circumferential surface of the second diameter portion of the safety valve housing; and the second unit is positioned under the gasket locking portion of the shaft, to seal the hole formed on the bottom of the second diameter portion of the safety valve housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features and advantages of the present invention will become more apparent to those of ordinary skill in the art by describing in detail preferred embodiments thereof with reference to the attached drawings in which: 
         FIG. 1  shows a valve stem housing, a safety valve housing, and a mounting cup where the valve stem housing and the safety valve housing are installed; 
         FIG. 2  is a cross-sectional view of the valve stem housing and the safety valve housing; 
         FIG. 3  illustrates a process of releasing excess pressure gas when a safety valve operates; 
         FIG. 4  shows a shaft of the safety valve; 
         FIG. 5  shows a stopper of the safety valve: 
         FIG. 6  shows a first gasket of the safety valve; 
         FIG. 7  shows a second gasket of the safety valve; and 
         FIG. 8  is a cross-sectional view of a safety vale according to a modified version of an embodiment of the present invention. 
     
    
    
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 [Description of numbers for constituents in drawings] 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 10: mounting cup 
                 11: notch 
               
               
                   
                 13: excess pressure gas outlet 
               
               
                   
                 20: valve stem housing 
                 21: protruding support unit 
               
               
                   
                 30: safety valve 
                 31: safety valve housing 
               
               
                   
                 32: shaft 
                 33: spring 
               
               
                   
                 34: stopper 
                 35: first gasket 
               
               
                   
                 36: second gasket 
               
               
                   
                   
               
             
          
         
       
     
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which a preferred embodiment of the invention is shown so that those of ordinary skill in the art can easily carry out the present invention. 
     The technical features of a safety valve to release excess pressure from a portable gas container for the prevention of an explosion according to the present invention are: A safety valve housing integrally formed with a valve stem housing is manufactured in a multiple cylinder shape, thereby sufficiently releasing an excess pressure gas from the container at once, to sufficiently lower the internal pressure of the container. Further, the location of an excess pressure gas outlet of the safety valve is arranged to be perpendicular to the line which connects the center of a mounting cup and a notch of the mounting cup. Therefore, when the valve stem housing and the safety valve housing integrally formed are injection-molded, it is possible to form a number of cavities in a mold in the same size, thereby remarkably reducing manufacturing cost. 
     In this application, the “safety valve  30 ” means to include all of a safety valve housing  31 , a shaft  32 , a spring  33 , a stopper  34 , a first gasket  35  and a second gasket  36 . The “safety valve housing  31 ” means a cylindrical shape having a first diameter portion  311  and a second diameter portion  312 . The location of an excess pressure gas outlet  13  is described as being arranged on the right or left of the center of a mounting cup  10 , to be perpendicular to the line connecting the center of the mounting cup  10  and a notch  11 . This arrangement is most desirable in terms of the manufacturing cost when injection-molding the valve stem housing and safety valve housing. Even if the excess pressure gas outlet  13  is not positioned on the right or left of the center of the mounting cup, it may be arranged between the excess pressure gas outlet  13  and the notch  11  as shown in  FIGS. 1 ( a ) and ( b ) . 
     The gas container where the safety valve  30  is installed comprises: a valve stem housing  20  and a safety valve housing  31  as integrally formed. The excess pressure gas outlet  13  formed in the mounting cup  10  is positioned on the right or left of the center of the mounting cup  10  which is perpendicular to the line connecting the center of the mounting cup  10  and the notch  11  (referring to  FIG. 1 ). Since the excess pressure gas outlet  13  is positioned in this manner and the valve stem housing  20  and the safety valve housing  31  are integrally formed &lt;referring to  FIG. 1 ( c ) &gt;, it is possible to form a number of cavities in a mold in the same size upon the injection-molding and therefore it is possible to remarkably reduce the manufacturing cost. 
     The portable gas container charged with the butane gas discharges the gas through a valve stem which is installed through the center of the mounting cup  10  connected to the top of the container. When the pressure in the container becomes higher than predetermined pressure, the excess pressure gas within the container is instantaneously and sufficiently released to the outside through the safety valve  30  of the present invention so that the pressure inside the container sufficiently lowers. The safety valve  30  basically comprises: the safety valve housing  31 , the shaft  32  positioned in the safety valve housing  31 , the stopper  34  fitted around a top end of the shaft  32 , the spring  33  fitted around a body of the shaft  32 , and first and second gaskets  35 ,  36  to prevent the leak of the gas. 
     The safety valve housing  31  has the first diameter portion  311  and the second diameter portion  312  which are different from each other in diameter. The first and second diameter portions  311 ,  312  are integrally formed. The constituent elements of the safety valve  30  are all arranged in the safety valve housing  31 . The diameter of the first diameter portion  311  is greater than that of the second diameter portion  312 . The first and second diameter portions  311 ,  312  are formed with a slope therebetween. An opening  313  to release the excess pressure gas is formed at a lower part of the second diameter portion  312 . 
     The shaft  32  is made of synthetic resin. The body  321  of the shaft  32  is made as a single shaft, to be positioned over the first and second diameter portions  311 ,  312  of the safety valve housing  31 . A top projection  324  is formed at a top of the body  321 . A gas outflow portion  322  and a gasket locking portion  323  are formed at a lower part of the body  321 . The gas outflow portion  322  needs a passage (space) to release the excess pressure gas. The passage through which the excess pressure gas releases may preferably include vertically penetrating grooves. These vertically penetrating grooves are each formed at the equidistant intervals, along the cylindrical surface of the edge of the gas outflow portion  322  (referring to  FIG. 4 ). 
     The diameter of the shaft  32  varies with the diameter of the shaft  32  above the gas outflow portion  322  being greater than the diameter of the shaft  32  under the top projection  324 . That is, the shaft  32  is formed such that the greater diameter of the body  321  of the shaft  32  is the same as the inner diameter of the spring  33 , to secure the spring  33  when the body  321  of the shaft  32  receives the spring  33 . Therefore, even though the spring  33  is compressed, it is able to maintain its position around the body  321  of the shaft  32 . 
     The stopper  34  is made of synthetic resin. As shown in  FIG. 5 , a lower part of the stopper  34  is open. A through-hole is vertically formed in the center of a closed upper part of the stopper  34 . A side wall is vertically formed, along the edge of the upper part of the stopper  34 . Vertically penetrating grooves which are the passages (space) to release the gas are formed at the equidistant intervals at the side wall. The outer circumferential surface of the side wall of the stopper  34  is positioned to be secured to the inner circumferential surface of the first diameter portion  311  of the safety valve housing  31 . The upper part of the shaft  32  insertedly penetrates the through-hole formed in the center of the upper part of the stopper  34 . Since the top projection  324  protrudes in the upper part of the body  321  of the shaft  32  (referring to  FIG. 4 ), even though the shaft  32  vertically moves, the shaft  32  inserted into the through-hole formed in the upper part of the stopper  34  does not leave the stopper  34 . That is, the shaft  32  is vertically movable, being inserted into the stopper  34 . Further, since the shaft  32 , spring  33 , stopper  34  and the second gasket  36  are assembled before these are inserted into the safety valve housing  31 , it is easy to keep. 
     The spring  33  is fitted around the outer circumferential surface of the body  321  of the shaft  32 , to be positioned between the gas outflow portion  322  of the shaft  32  and the upper part of the stopper  34 . When the pressure inside the container is normal, the elasticity of the spring  33  pushes the shaft  32  downwardly so that the second gasket  36  is secured to the center of the bottom of the second diameter portion  312  of the safety valve housing  31 , thereby preventing the gas which tends to flow out through the opening  313  from flowing out. 
     The first gasket  35  is made of a kind of rubber having elasticity. The first gasket  35  is inserted between an upper end of the first diameter portion  311  of the safety valve housing  31  and the excess pressure gas outlet  13  of the mounting cup  10 , to seal so that the gas inside the container cannot leak or escape through the excess pressure gas outlet  13 . 
     The second gasket  36  is made of a kind of rubber having elasticity. A body  362  of the second gasket  36  has a bottom side being closed and a top side being open. A side wall is formed upwardly in a cylindrical shape, along the edge of the bottom side. A protruding portion  361  having a circular cross section is formed at an upper end of the side wall (referring to  FIG. 7 ) (However, the cross section of the protruding portion may be in a D-shape instead of the circular shape.) 
     The body  362  of the second gasket  36  is positioned around the gasket locking portion  323  formed at the lower part of the shaft  31 . As the part protruding inwardly from the protruding portion  361  of the second gasket  36  is fitted into a gap between the gas outflow portion  322  and the gasket locking portion  323 , the upper end of the protruding portion  361  is positioned to be secured to the lower side of the gas outflow portion  322 . 
     When the pressure of the gas charged in the gas container is normal, the second gasket  36  seals double since the bottom side of the body  362  of the second gasket  36  closes the opening  313  formed on the lower part of the second diameter portion  312  and the protruding portion  361  comes into contact with the inner circumferential surface of an upper part of the second diameter portion  312  of the safety valve housing  31 . However, when the second gasket  36  operates by the excess pressure gas in the gas container and it is forced to move upwardly to the maximum, the second gasket operates so that the protruding portion  361  of the second gasket  36  moves from the upper part of the second diameter portion  312  of the safety valve housing  31 . 
     Furthermore, when the excess pressure gas occurs in the container, the protruding portion  361  at the upper end of the second gasket  36 , which seals the upper part of the inner circumferential surface of the second diameter portion  312  of the safety valve housing  31 , separates from the inner circumferential surface of the second diameter portion  312 . Then, since the area receiving the pressure of the excess pressure gas increases (that is, the entire lower side of the body of the second gasket is pressed) and much greater force is applied, the shaft  32  being locked with the second gasket  36  moves up. Then, the protruding portion  361  of the second gasket  36  moves from the upper part of the second diameter portion  312  and moves until the spring  33  is compressed to the maximum, making a sufficient space where the excess pressure gas can release. Then, the excess pressure gas instantaneously sufficiently releases at once to enough lower the pressure inside the container. 
       FIG. 8  shows a safety valve with a second gasket  36 ′ according to a modified version of the embodiment of the present invention. The second gasket  36 ′ is separated into two constitutions, a first unit  361 ′ and a second unit  362 ′: The first unit  361 ′ has an O-ring shape (The cross-section of the O-ring shape may not be circular and it may be in a D-shape.) When the internal pressure of the container is normal, the first unit  361 ′ is inserted between the gas outflow portion  322  and the gasket locking portion  323 ′ of the shaft  32 , so that its outer circumferential surface is secured to the inner circumferential surface of the second diameter portion  312  of the safety valve housing  31 . The second unit  362 ′ is to seal the opening  313  formed on the lower part of the second diameter portion  312  of the safety valve housing  31 . Since the rest of the description is the same as that of the second gasket  36  described above, no further description is presented. 
     Another characteristic constitution of the present invention is that a plurality (properly, about three (3)) of protruding support units  21  are formed to protrude outwardly at an upper part of the outer circumferential surface of the valve stem housing  20 . When the valve stem housing  20  and the safety valve  30  are installed to the mounting cup  10 , since the plurality of the protruding support units  21  come into contact with the lower side of the mounting cup  10 , these support to maintain the sealing condition of the first gasket  36  which seals the gap between the upper end of the safety valve housing  31  and the excess pressure gas outlet  13  formed in the mounting cup  10  in any situations or conditions. 
       FIG. 3  illustrates the operational mechanism of the safety valve for the gas container according to the present invention. When the pressure of the gas inside the container is normal, the shaft  32  is pushed downwardly by the elasticity of the spring  33  in the initial stage, so that the second gasket  36  is secured to the bottom of the second diameter portion  312  of the safety valve housing  31 , to seal the opening  313  and prevent the gas inside the container from flowing out through the opening  313 . 
     After that, when the pressure of the gas inside the container gradually increases and therefore the second gasket  36  positioned at the lower position of the shaft  32  is slightly pushed upwardly, since the cross-sectional area of the second diameter portion  312  is greater than the opening  313  formed on the lower part of the second diameter portion  312  of the safety valve housing  31 , the area under the body  362  of the second gasket  36 , which is pressed by the gas, increases. Therefore, as the force which the shaft  32  receives by the gas pressure increases, the second gasket  36  is pushed to the upper part of the second diameter portion  312  of the safety valve housing  31 . In the first diameter portion  311 , since its diameter is greater than that of the second diameter portion  312 , the excess pressure gas sufficiently instantaneously releases at once, to sufficiently lower the pressure inside the container. 
     The excess pressure gas hardly releases before the protruding portion  361  of the second gasket  36  is pushed to the upper part of the second diameter portion  312  of the safety valve housing  31 . However, as soon as the protruding portion  361  of the second gasket  36  passes the upper part of the second diameter portion  312  of the safety valve housing  31 , the inner diameter of the safety valve housing  31  increases and the passage to release the gas increases, so that the excess pressure gas is temporally sufficiently released. Accordingly, the pressure inside the gas container drops below the set pressure and the gas container returns to the normal state. The safety valve  30  according to the present invention operates in this manner. After the excess pressure gas is once released, the pressure inside the container does not keep a dangerous condition around the set pressure unlike the conventional safety valve. The safety valve  30  according to the present invention lowers the pressure inside the container to within a safe range. 
     In the safety valve to release the excess pressure from the portable gas container for the prevention of an explosion according to the present invention, since the safety valve housing is formed in the multiple cylinder shape, the area which the excess pressure gas comes into contact with the lower side of the second gasket increases and therefore the force which the second gasket receives from the excess pressure gas increases, to sufficiently and instantaneously release the excess pressure gas inside the container at once and to sufficiently lower the pressure inside the container. In addition, since the protruding support units are formed at the valve stem housing, these support units support to prevent the safety valve housing from tilting to one side, so that the first gasket positioned between the safety valve housing and the mounting cup can always keep the compressed condition. This prevents the liquid gas from leaking between the excess pressure gas outlet of the mounting cup and the first gasket. 
     Further, in accordance with the safety valve of the present invention, the excess pressure gas outlet is positioned to the right or left of the center of the mounting cup, which is perpendicular to the line connecting the center of the mounting cup and the notch. Therefore, when the valve stem housing and the safety valve housing as integrally formed are injection-molded, it is possible to form a number of cavities in the mold in the same size, to remarkably reduce the manufacturing cost. In addition, all constituent elements of the safety valve are assembled in advance and inserted in the safety valve housing. In this regard, assembling is simple and productivity is very high. 
     The invention has been described using preferred exemplary embodiments. However, it is to be understood that the scope of the invention is not limited to the disclosed embodiments. On the contrary, the scope of the invention is intended to include various modifications and alternative arrangements within the capabilities of persons skilled in the art using presently known or future technologies and equivalents. The scope of the claims, therefore, should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.