Patent Publication Number: US-2011062157-A1

Title: System for pressure release from a closed container and a container for use therefore

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from German Patent Application Serial No. 20 2009 012 542.4, filed Sep. 17, 2009, the entire contents of which is herein incorporated fully by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a safety device for releasing pressure from closed containers when heated. More specifically, the present invention relates to a disk or plate for covering the opening of a container, wherein the disk or plate dissolves at a particular temperature threshold so as to release pressure within the container when heated. 
     2. Description of the Related Art 
     When fluids are transported in closed containers, considerable pressure can build up in the interior of the containers, particularly if the container is heated; this can ultimately cause the container to burst. For this reason, for example, in trade-law regulations with regard to construction of metallic intermediate bulk containers (IBC) for carriage of hazardous fluids, provision of a device to release pressure is mandatory. The purpose of these regulations is to prevent bursting, and thus uncontrolled release of the hazardous fluid into the environment. 
     What is not appreciated by the prior art is that, until now, as a rule, spring-loaded valves have been used for pressure release. These valve types have a series of substantial disadvantages. 
     Proper functioning of such a valve for pressure release when heated, of necessity pre-supposes that the response pressure at which spring force is overcome is relatively low. Typically, an excess pressure of 20,000 Pa to 65,000 Pa is enough to make the valve respond. However, these pressure thresholds are exceeded, for example, when the container is subject to mechanically-induced pressure spikes during transport and loading, so that the valve opens in undesired fashion and fluid can splash out of the opening. Thus, such an IBC cannot travel if fully sealed. 
     A further disadvantage arises from the fact that customarily used spring-loaded valves, especially any sealing elements such as rubber that are present in the valves, are not resistant to numerous filling media. This results in a considerable expense for maintenance. 
     Accordingly, there is a need for a simpler and more cost-effective device for pressure release of closed containers when heated, and a simpler and more cost-effective small container with a pressure release device. 
     ASPECTS AND SUMMARY OF THE INVENTION 
     An aspect of the present invention is to provide a simpler and more cost-effective device for pressure release of closed containers when heated. 
     Another aspect of the present invention is to provide a simpler and more cost-effective small container with a pressure release device. 
     The invention-specific safety device for pressure release of a closed container when heated has at least one ventilation opening, a covering disk or plate made of a material that melts at a critical temperature, sealing the ventilation opening, and an affixing device for the disk or plate that covers the ventilation opening. Taken by itself, in the absence of the disk or plate, the affixing device must permit the fluid to emerge from the container through the ventilation opening into the environment. This is the case for example if an at least partially fluid-permeable affixing device is utilized; but, also if, for example, the disk or plate is securely glued on the edge of the ventilation opening or securely clamped at discrete locations on the edge of the ventilation opening. 
     The pressure in the interior of a closed container is dependent on the temperature in the interior of the container. When the container is heated, the pressure rises, which, upon reaching a pressure limit value and thus a limit temperature, could cause the container to burst and the container&#39;s contents to come out in uncontrolled fashion. The limit temperature for a given container is dependent on the properties of the container and the fluid with which it is filled; this can, for example, be determined in combustion tests. 
     As the critical temperature according to this invention, a temperature is to be understood that lies some degrees Celsius below the limit temperature, to ensure that the melting process has been sufficiently completed so that the pressure has been equalized as necessary before the limit temperature is reached. 
     Until the critical temperature has been reached, the disk or plate seals the ventilation opening. The affixing device prevents the plate or disk from slipping or shifting, which could cause the ventilation opening to be opened in undesired fashion. 
     When the critical temperature is reached, the disk or plate melts and uncovers the ventilation opening, so that the affixing device taken by itself, i.e. in the absence of the disk or plate, allows fluid to exit from the container through the ventilation opening into the environment, and the pressure can be equalized via the ventilation opening. 
     Plastic is an especially suitable material for the disk or plate due to its good resistance to a number of typical filling materials and due to good adaptability of melt temperatures. PTFE (polytetrafluoroethylene), in particular, has proven itself for many typical applications. 
     Fundamentally, the time needed for the actual opening of at least a part of the ventilation opening, between the onset of the melting process and the plate or disk melting through, is dependent on their geometry, especially their thickness. This results in a relationship of tension between a required minimum stability of the disk or plate that should be able to support itself and resist disruptive influences from without, and a delay that results from the onset of pressure equalization. However, this problem can be solved if the disk or plate has at least one recess and/or an enclosed groove in the area of the ventilation opening. 
     The recess results in a thinner partial section of the disk or plate that correspondingly melts through and can cause pressure equalization more quickly than the rest of the disk or plate, which ensures the desired stability. Instead of a staged recess, it is also possible to provide a continuous variation in thickness in an appropriate area of the disk or plate, so that in case the temperature fails to drop, the opening available for pressure equalization gradually increases further. 
     Providing an enclosed groove, i.e. a channel-like recess in the material of the disk or plate, whose starting point connects to its end point, permits a relatively large opening to be provided by melting away a relatively small amount of material, namely the base of the groove, which results when the base of the groove melts away, and the section of the disk or plate surrounding the groove drops out. 
     An advantageous additional effect is achieved if the disk or plate is manufactured from a material suitable to carry advertising or a logo. Alternatively, it is also possible to apply a logo as a relief-like recess into the disk or plate. 
     One especially simple-to-produce embodiment form of the securing device can result by placing the ventilation opening at one end of a ventilation pipe which is at least partially overlapped by the affixing device. 
     To make it possible to replace a damaged or molten disk or plate, provision is made that the end of the ventilation pipe and the affixing device be detachably connected to each other. 
     This can be technically implemented with especial ease if the ventilation pipe is a pipe with an overall circular cross section that is provided on the end overlapping the affixing device with an exterior threading; that the affixing device is a sleeve nut adapted to the exterior threading, and that the detachable connection be made by screwing the sleeve nut on the exterior threading. With this, overall cross section means that it does not need to have the inner cross section of the opening that impinges in the pipe of this feature, but rather the interior cross section and the cross section including the cross section of the pipe wall. 
     The invention-specific small container has a rack and a vessel situated within the rack with at least one ventilation opening and at least one device for pressure release, situated at the at least one ventilation opening of the container. According to the invention, the device for pressure release has a disk or plate covering the ventilation opening consisting of a material that melts below a critical temperature, and an affixing device for the disk or plate covering the ventilation device. Taken by itself, in the absence of the disk or plate, the affixing device must permit the fluid to emerge from the container through the ventilation opening into the environment. This is the case for example if an at least partially fluid-permeable fixing device is utilized, but also if for example the disk or plate is securely glued on the edge of the ventilation opening or securely clamped at discrete locations on the edge of the ventilation opening. 
     Until the critical temperature has been reached, the disk or plate seals the ventilation opening. The affixing device prevents the plate or disk from slipping or shifting, which could cause the ventilation opening to be opened in undesired fashion. When the critical temperature is reached, the disk or plate melts and releases the ventilation opening, so that the affixing device taken by itself, i.e. in the absence of the disk or plate, allows fluid to exit from the container through the ventilation opening into the environment, and the pressure can be equalized via the ventilation opening. 
     It is especially advantageous if the small container has a vessel with more than one ventilation opening and/or an additional filling opening. It is especially favorable to place one of the ventilation openings on the upper side of the vessel. 
     Plastic is an especially suitable material for the disk or plate due to its good resistance to a number of typical filling materials and due to good adaptability of melt temperatures. PTFE (polytetrafluoroethylene), in particular, has proven itself for many typical applications. 
     For the reasons already discussed above, it is advantageous if, in the area of the ventilation opening, the disk or plate has at least one recess and/or an enclosed groove. The recess and/or enclosed groove results in a thinner partial section of the disk or plate that functions as a stress concentrator and also correspondingly melts through at a different rate due to lower mass and thermal transfer and can cause pressure equalization more quickly than the rest of the disk or plate, which ensures the desired stability. Instead of a staged recess, it is also possible to provide a continuous variation in thickness in an appropriate area of the disk or plate, so that in case the temperature fails to drop, the opening available for pressure equalization gradually increases further. Owing to melting through of a small area, the groove quickly allows a large opening to become available for the pressure equalization, as was explained above. 
     An advantageous side effect is achieved if the disk or plate is manufactured from a material suitable to carry advertising or a logo. Alternatively, it is also possible to apply a logo as a relief-like recess into the disk or plate. 
     One especially simple-to-produce embodiment form of the safety device can result by placing the ventilation opening at one end of a ventilation pipe which is at least partially overlapped by the affixing device. 
     To make it possible to replace a damaged or molten disk or plate, provision is advantageously made that the end of the ventilation pipe and the fixing device be detachably connected to each other. 
     This can be technically implemented with especial ease if the ventilation pipe is a pipe with an overall circular cross section that is provided on the end overlapping the affixing device with an exterior threading; that the affixing device is a sleeve nut adapted to the exterior threading, and that the detachable connection be made by screwing the sleeve nut on the exterior threading. Overall cross section means that it does not need to have the inner cross section of the opening that impinges in the pipe of this feature, but rather the interior cross section and the cross section including the cross section of the pipe wall. 
     The above, and other aspects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of the safety device of the present invention. 
         FIG. 2   a  is a perspective view of a disk of the safety device as shown in  FIG. 1 . 
         FIG. 2   b  is an angled view from above of the disk of the safety device from  FIG. 2   a.    
         FIG. 3  is a perspective view of a container employing the safety device of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to several embodiments of the invention that are illustrated in the accompanying drawings. Wherever possible, same or similar reference numerals are used in the drawings and the description to refer to the same or like parts or steps. The drawings are in simplified form and are not to precise scale. For purposes of convenience and clarity only, directional terms, such as top, bottom, up, down, over, above, and below may be used with respect to the drawings. These and similar directional terms should not be construed to limit the scope of the invention in any manner. The words “connect,” “couple,” and similar terms with their inflectional morphemes do not necessarily denote direct and immediate connections, but also include connections through mediate elements or devices. 
     Turning first to  FIG. 1 , there is shown an embodiment example of the safety device  10  according to present invention where a housing wall  15  of a container (see  FIG. 3 ) is penetrated by a ventilation opening situated at the end of a ventilation pipe  11  with an overall circular cross section, connected with the housing wall. The ventilation opening itself is not perceptible in  FIG. 1 , since it is covered by a disk  13  which covers the ventilation opening in sealing fashion. The disk is made of a material that melts at a critical temperature. It is adapted to an exterior thread  14  made on the overlapping end of ventilation pipe  11 , whose lowest threading can be seen in  FIG. 1 , and engages with the ventilation pipe by being screwed on. The sleeve nut  12  fixes the disk  13  in place. In the area of its borehole, it is fluid-permeable. 
     If the temperature rises at least to the critical temperature in the interior of the container, disk  13  melts and the pressure is equalized, which prevents the vessel from bursting. 
     Turning then to  FIG. 2   a , there is shown is a view of the disk of the safety device  10  from  FIG. 1 . Disk  13  has a recess  21  and an island  23  formed by an enclosed groove  22 . Recess  21  and closed groove  22  are shown as being shaded, to clarify the difference in level to the surface of disk  13  facing toward the viewing direction. The shaded areas are at a greater distance from the viewer, at these places the material of the disk is thus thinner. This makes it possible for these areas of disk  13  to melt through more quickly and thus equalize the pressure more rapidly, when the critical temperature has been reached. Additionally, in the case of enclosed groove  22 , what is attained is that the entire area defined by island  23  opens up, if the base of enclosed groove  22  has melted away. 
     With reference to  FIG. 2   b  there is shown an angled view from above of the embodiment form of a disk of the safety device of  FIG. 2   a ; and, as in  FIG. 2   a , the disk  13  is shown with recess  21  and island  23  formed by enclosed groove  22 . Recess  21  and enclosed groove  22  are also depicted with shading in  FIG. 2   b , to clarify the difference in level of the surface of disk  13  facing the viewing direction. 
     As can be seen in  FIG. 2   b , the side wall  24  of recess  21  and the side wall  25  of the closed groove can be recognized, which elucidate that the shaded areas, due for example to a stamping process during the manufacture of disk  13 , lie lower relative to the side of disk  13  facing the viewer, and thus this area of disk  13  is not as thick. 
     As can be readily determined by the above description of  FIGS. 2   a  and  2   b , the pressure sensitive disk or plate has varied stress concentrations based on the geometry of the patterns that are formed in the disk or plate (the pressure seal). These concentrations allow certain portions of the pressure seal to melt before other portions. This factor is important in regulating the release of pressure according to actual pressure conditions. Additionally, this serves the purpose of allowing varying liquid types, under varied pressure conditions, to utilize the container, though not necessarily at the same time. The pressure seal of the present invention can be manufactured in such a way as to accommodate various logos or patterns which can be designed in such a way as to optimize the pressure release characteristics of the pressure seal. 
     Turning then to  FIG. 3 , there is shown a cross section through an invention-specific small container  100  where there is further shown a rack  111  composed of upright piping  112 , base frames  113 , stacking frames  114 , and a container  115 . 
     The top side of container  115  is penetrated by a filling opening designed as a filling pipe  116 , and two ventilation openings  117 ,  118  designed as ventilation pipes. Ventilation opening  117  is closed by a blind flange  119 , ventilation opening  118  is part of a safety device as was explained in  FIG. 1 , of which, however, next to ventilation pipe  118  only the sleeve nut  120  is visible in the  FIG. 3  depiction. Additionally, the vessel of small container  100  has an optional outlet pipe. 
     In the claims, means or step-plus-function clauses are intended to cover the structures described or suggested herein as performing the recited function and not only structural equivalents but also equivalent structures. Thus, for example, although a nail, a screw, and a bolt may not be structural equivalents in that a nail relies on friction between a wooden part and a cylindrical surface, a screw&#39;s helical surface positively engages the wooden part, and a bolt&#39;s head and nut compress opposite sides of a wooden part, in the environment of fastening wooden parts, a nail, a screw, and a bolt may be readily understood by those skilled in the art as equivalent structures. 
     Having described at least one of the preferred embodiments of the present invention with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various changes, modifications, and adaptations may be effected therein by one skilled in the art without departing from the scope or spirit of the invention as defined in the appended claims.