Abstract:
An approach is provided for minimizing failure of relief valve assembly and enhancing quality of control of making a relief valve conforming to the standards. An improved relief valve includes a body having a seat formed in a passageway. A relief valve core member is mounted in the seat, wherein the body and the relief valve core member are fixedly engaged by spinning the body into a receiving portion of one the relief valve member, wherein the relief valve member is configured to create a resilient force that control the pressure on the passageway.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a relief valve, and more particularly to a relief valve unit for a pressure cylinder. 
       BACKGROUND 
       [0002]    Conventional disposable pressure cylinders have been used to contain various kinds of gas (e.g., LP (Liquefied Petroleum) or liquefied petroleum gas mixed with methylacetylene-propadiene gas (called as MAPP gas), etc.). These cylinders include a main valve to control high pressured sources. For safety purposes, safety means are regulated by various agencies such as a Department of Transportation (DOT), a relief valve conforming to the safety standard is inserted into each compressed cylinders. 
         [0003]    The relief valve is a type of valve used to control or limit the pressure in a system by allowing the pressure source (e.g., fluid or gas) to flow from an auxiliary passageway, away from the main flow path. The relief valve is designed or set to open at a predetermined pressure to protect pressure vessels and other equipment from being subjected to pressures that exceed their design limits. When a pressure setting is exceeded, the relief valve becomes the path of least resistance as the valve is forced open and a portion of the fluid is diverted through the auxiliary route. The diverted sources (liquid, gas, or liquid-gas mixture) are usually routed through a valve body system via a passageway. 
         [0004]    Pressure relief valves are self-actuated safety valves designed to relieve excess pressure upstream from the line. The Compressed Gas Association (CGA) is involved in the development and promotion of safety standards and safe practices in the industrial and medical gas industry. The CGA publishes standards and specifications regarding gas cylinders, equipment, gases, hydrogen, medical, protection and safe handling and pressure relief devices; such standards are widely adopted in the United States and other areas of the world. 
         [0005]    Conventionally, a relief valve body consists of threaded portions at which the relief valve body and the relief valve core are firmly engaged. For example, in the assembly line, the valve body and relief valve core are jointly engaged with the threads by screwing the relief valve core down into the body. As an exemplary shown in the  FIGS. 7 and 8 , shown as backgrounds, the relief valve body includes the threads (e.g., helical ridge)  701  resided inside of the wall of the body. In order for threadly fastening the relief valve core and the body  801 , the relief valve core includes a head having grooves or threads  703  formed on outer surface of the head. Also, the head is specially shaped to allow a screwdriver to grip the screw when driving in it. Thus, when assembling, the relief valve core is fastened into the body by using a method that the relief valve core is screwed down until a gasket touches the bottom of relief valve body. As shown in the  FIG. 8 , the completion of the conventional assembly of the relief valve being disposed into a cylinder is provided. 
         [0006]    These conventional systems have certain drawbacks from a manufacturing standpoint. First, leakage of pressured source can be caused by metallic dust or chips brought from screwing process through threads during assembly. Second, it is a challenge to determine and control the insert depth when the relief core is threadly engaged into the relief valve body, 
         [0007]    With regard to the first issue, typically, due to a short assembly line cycle time, the relief valve core is inserted by an automatic process in the relief valve body. A revolving screwdriver hangs over the assembly line and when the cylinders are aligned the screw comes down to screw the relief valve core to the valve body by utilizing the threads on both sides. During the process, the slightest imperfection or misalignment can lead to defects. Also, friction created by abrasion of the threads can create micro chips and metallic dusts, thereby preventing the gasket from sealing properly. This causes seepage of gas from the relief valve unit. 
         [0008]    As for the second issue, the insertion depth is critical. This is because of the fact that the force constant of the spring disposed in the relief valve core is determined by the insert depth and the constant is related to open the relief valve core to release the pressured source. If the insert depth is too shallow the spring of the relief valve core does not have sufficient force to press the rubber gasket causing the relief valve core to release before reaching to a predetermined pressure level (e.g., 360-450 PSI (Pound-force per Square Inch) set by the CGA). However, if the inserted depth of the relief valve core is too deep, the opening tolerance of the relief valve core increases surpassing the level of releasing. 
         [0009]    Moreover, it may not be feasible or nearly impossible to inspect the insert depth of each and every relief valve unit once the assembly is completed. For instance, cylinder manufacturers inspect only two per each assembled 3000 cylinders to meet the DOT regulations. However, the irregularities of insertion depths cannot guarantee that the remaining cylinders are acceptable. 
         [0010]    Accordingly, a need exists for providing a relief valve unit that overcomes drawbacks of conventional assembly process. 
       SOME EXEMPLARY EMBODIMENTS 
       [0011]    These and other needs are addressed by the claimed invention in which an apparatus is provided for minimizing non-conforming relief valve when assembling a relief valve member into a valve body for installation into a cylinder. The claimed apparatus includes a relief valve body in which the relief valve member is engaged without using threads for the engaging, wherein a head of the relief core member is fixedly engaged into the valve body using a spinning process. In the spinning process, the top ends of the valve body can be spun into the inside of grooved belt formed at the circumference of the head of the relief valve member to engage the relief valve core member and the valve body. This arrangement provides an assembly process that is simple and cost-effective, while enhancing the quality control. 
         [0012]    According to one aspect of the present invention, a pressure relief device is provided. The device includes a relief valve core member configured to relieve the pressure in response to a predetermined pressure level. The device includes a valve body configured to receive the relief valve core member, wherein the valve body includes a extended opening passageway having a first end, a tube, and a second end, wherein a bottom part of the relief valve core member is positioned at the second end, and the middle part of the relief core member is resided at the tube, wherein the first end of the valve body has a insert portion configured to engage the insert portion into a receiving portion formed at a top part of the relief valve core member. The relief valve core member further includes a valve pin, a spring resides over an outside diameter of the valve pin, a head resides on the first end of the valve body and configured to receive the insert portion formed at the first end, and a gasket configured to engage on the second end, wherein the relief valve core member and the valve body is securely engaged to resiliently compress the pressure through the interaction of the spring and gasket against sealing surface of the second end. 
         [0013]    In another aspect of the invention, an apparatus to control a pressure is provided. The apparatus includes a body having a seat formed in a passageway; and a relief valve member mounted in the seat, wherein the body and the relief valve member are fixedly engaged by spinning the body into a receiving portion of the relief valve member, wherein the relief valve member is configured to create a resilient force that control the pressure on the passageway. 
         [0014]    The relief valve core member further includes a valve pin; a spring resides over an outside diameter of the valve pin; a head configured to receive the upper part of the valve pin is formed of the receiving portion; and a gasket configured to receive the bottom part of the valve pin, wherein the receiving portion of the head fixedly engaged with the valve body resiliently compresses the pressure through the interaction of the spring and gasket against sealing surface on the passageway. 
         [0015]    In yet another aspect of the present invention, a method for assembling a relief valve is disclosed. The method provides determining a body having a seat for receiving a relief valve member and openings for relieving a pressure; assembling a relief valve member according to a predetermined pressure, wherein a spring is disposed outside of a valve pin, a gasket and a head is engaged at each other side of the valve pin; disposing the relief valve member within the seat; engaging the body with the relief valve member, wherein the portions of the body is spun into a engaged portion formed at the head of the relief valve member; placing the engaged relief valve within a housing formed in the cylinder vessel; and sealing the housing. 
         [0016]    Still other aspects, features, and advantages of the present invention are readily apparent from the following detailed description, simply by illustrating a number of particular embodiments and implementations, including the best mode contemplated for carrying out the present invention. The present invention is also capable of other and different embodiments, and its several details can be modified in various obvious respects, all without departing from the spirit and scope of the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which: 
           [0018]      FIG. 1  is a diagram showing a sectional front view of a relief valve body in accordance with an embodiment of the present invention; 
           [0019]      FIG. 2  is a diagram of a relief valve core member which is engaged into the relief valve body of  FIG. 1 , in accordance with an embodiment of the present invention; 
           [0020]      FIG. 3  is a diagram showing a top and front view of a head of the relief valve core member, in accordance with an embodiment of the present invention; 
           [0021]      FIGS. 4A-4C  are diagrams showing a spinning process by which the head of the relief core member can be engaged with the relief valve body, in accordance with an embodiment of the present invention; 
           [0022]      FIG. 5  is a diagram of an assembled relief valve in which the relief valve core of  FIG. 2  is engaged into the relief valve body of the  FIG. 1  by using the spinning process, in accordance with an embodiment of the present invention; 
           [0023]      FIG. 6A  is a sectional front view of the assembled relief valve of  FIG. 5  disposed into a cylinder, in accordance with an embodiment of the present invention; 
           [0024]      FIG. 6B  is a flowchart of a process for assembling relief valve, in accordance with an embodiment of the present invention; 
           [0025]      FIG. 7  is a diagram showing a conventional relief valve core member and a relief valve body; and 
           [0026]      FIG. 8  is a diagram showing a conventionally assembled relief valve into a cylinder. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0027]    A device, and method for assembling a relief valve core member into a valve body and the assembled relief valve are described. In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It is apparent, however, to one skilled in the art that the present invention may be practiced without these specific details or with an equivalent arrangement. In other instances, well-known structures and devices are shown in block diagram form in order to avoid unnecessarily obscuring the present invention. 
         [0028]      FIG. 1  is a diagram showing a sectional front view of a relief valve body in accordance with an embodiment of the present invention. The valve body  100 , which is adapted to be engaged a relief valve core member, includes a first end as an outlet  101 , a second end as an inlet  103  and a longitudinal tube  105  configured between the first end  101  and the second end  103 . The first end  101 , a longitudinal tube  105  and a second end  103  are configured in-line for releasing the pressured source through the outlet  101 . In an exemplary embodiment, the valve body can be made of one of brass, cast iron, carbon steel, stainless steel, or synthetic material. The material of body can endure a set pressure and the set pressure for the valve, for example, can range from about 360 to about 450 PSI. 
         [0029]      FIG. 2  is a diagram showing a relief valve core member  200 , in accordance with an embodiment of the claimed subject matter. The relief valve core member  200  includes a head  207 , a valve pin  201 , a spring  203  and a rubber gasket  205 . In an exemplary embodiment, the valve pin  201  can be made one of brass, cast iron, carbon steel stainless steel, or synthetic material. Diameter of the valve pin  201  can be varied according to a predetermined pressure force. For example, the diameter of the valve pin can be about 1.6 mm-1.8 mm. The spring  203 , which is disposed on the outside of the valve pin  201 , resides between the head  207  and the rubber gasket  205 . The spring  203  pushes the rubber gasket  205  downward against the second end  103  to seal off a seat of the rubber gasket  205 . In an embodiment, the rubber gasket  205  includes a cup  213  and a rubber  215  (e.g., natural rubber, hydrin rubber, or neoprene, etc.) disposed inside being covered by the cup  213 . The different force constant of the spring  203  can be selected according to a predetermined relief level (e.g., 360-450 PSI). Any biasing mechanisms other than the spring  203  can be applied. According to an exemplary embodiment, the spring  203  can be made of a piano wire. The piano wire can be made from tempered high-carbon steel or brass. Example of materials that may be used as part of the spring include coil of wire, steel or rubber and are not limited to this construction. It is noted that the spring  203  may be any elastic material that works to regain its original shape after being compressed. As shown in the  FIG. 2 , the head  207  includes a tube  211  disposed inside of the head to receive the valve pin  201 . The head  207  also has a grooved belt  209  at the circumference of the head  207  to engage the valve body  100  by using a spinning process shown in the  FIG. 4A-4C . 
         [0030]      FIG. 3  is a diagram showing a top and front view of a head, one of the relief valve core member, in accordance with an embodiment of the present invention. As shown in the top view, in the middle of the cross, a first hole  303  is disposed for relieving pressured gas to a vertical direction to the head position through passageway made from the second end  103  to the first end  101  when the rubber gasket is opened provided the predetermined level of the force is reached. In the top view of the head  207 , cross-head groove (“+” shaped slot)  301  is formed for facilitating to relieve the pressured gas from a second hole  305  that is relieved from a horizontal direction. The relieved gas from the second hole can flow to openings formed at the “+” shaped slot  301  to be relieved through the hole  303 . According to an exemplary embodiment, the head  207  can be made of tempered high-carbon steel or brass. In an embodiment, diameter of the head  207  can be about 8.5 mm-9 mm. 
         [0031]      FIGS. 4A-4C  are diagrams showing a spinning process by which the head of the relief core member can be engaged with the relief valve body, in accordance with an embodiment of the present invention. In this process, the valve body  100  is disposed in the  FIG. 4A . In  FIG. 4  B, the bottom portion of the head  207  is inserted into the valve body  100  through the first end  101  of the valve body  100 . The position of the head  207  is set to receive top portions  401  of the valve body  100  via grooved belt  209 . As shown in the  FIG. 4C , a spinning process can be achieved by folding the top portions  401  of the vale body  100  and spinning into the inside of the grooved belt  209  formed at the circumference of the head  207 . In this process, the head  207  of the relief valve core member  200  and the valve body  100  can be firmly engaged. 
         [0032]      FIG. 5  is a diagram of an assembled relief valve  500  in which the relief valve core of  FIG. 2  is engaged into the relief valve body of the  FIG. 1  by using the spinning process ( FIGS. 4A-4C ), in accordance with an embodiment of the present invention. As shown in the  FIG. 5 , the engaged portion need not include any threads, spikes or grooves outside of the relief valve core member  200 . As shown, no threads, spikes or grooves are formed inside of the valve body  100  to allow for engaging the relief valve core member  200 . An O-ring  503  is disposed at the bottom of the head in order to seal off spaces on a valve seat where the engaged relief valve  500  is installed into a cylinder. 
         [0033]    According to the disclosed spinning process shown in the  FIGS. 4A-4C , the grooved belt  209  formed at the circumference of the head  207  allows to simply engage the relief valve core member  200  and the relief valve body  100  by folding the first end  101  of the valve body  100  inside of the grooved portions  209  when assembly. The spinning process causes the head  207  being prevented from easily becoming disengaged from the engaged portion  401 . Therefore, the engaged portion  401  allows to sustain resilient force caused by a compressed spring  207  when assembling the relief valve core member  200  into the valve body  100 . 
         [0034]    According to an embodiment, the second end  103  of the relief valve body  100  defines portions  505  for receiving the rubber gasket  205  (See,  FIG. 5 ) which is placed at the bottom of the relief valve core member  200 . As shown in the  FIG. 5 , the assembled relief valve  500  includes the valve pin  201 , the helical spring  207  and the rubber gasket  205 . The rubber gasket  205  is disposed at the second end  103  of the valve body  100 . According to an embodiment, the rubber gasket  205  includes the rubber portion  215  to be slid into the cup  213  that extends away from an appropriate end of the portion  505  of the valve body  100 . The gasket  205  abuts on the portion  505  which bears against the respective compressed force from the compressed spring  203  disposed outside of the valve pin  201  of the relief valve core member  200 . 
         [0035]    A rubber element  215  of gasket  205  is sealingly engaged against the receiving portions  505  of the valve body  100 . When pressure builds up in the relief valve core member  200  and it exceeds a predetermined level, the force is exerted to the rubber gasket  205  and the rubber portion  211  can be opened by the force. At that point, a certain amount of the compressed pressure will be permitted to relieve through the passageways formed in the longitudinal tube  105 , first end  101  of the valve body  100  and the circled hole  303  of the head  207 . It is noted that the diameter of the longitudinal tube  105  can be determined by the level of predetermined force associated with a size of cylinder. In an exemplary embodiment, the diameter of the longitudinal tube  105  ranges about 4.7 mm-4.9 mm. 
         [0036]      FIG. 6A  is a sectional front view of the assembled relief valve  500 , as shown in  FIG. 5 , disposed into a cylinder, in accordance with an embodiment of the present invention. Main valve  601  is disposed on a cylinder chamber. Washer  603  is used to support and to lock the load of the assembled relief valve  500 . For the purpose of mechanical seal, for example, a steel washer  603  having a slit in the middle of the washer is disposed on the top of the head  207  to cover the housing  607 . It is noted that relieved gas is discharged through the slit. The washer  603  can be metal or plastic. The assembled relief valve  500  is inserted into the housing  607  formed to receive the assembled relief valve  500 . In this example, an O-ring seat  609  is defined in the middle portion of the housing. The O-ring  503  is positioned in the O-ring seat  609  to receive and sealingly to engage the assembled relief valve  500  and the housing of the cylinder  607 . At that point, the O-ring  503  can be recessed to perform a mechanical seal. The seal is designed to have a point contact between the O-ring  503  and sealing faces. This allows a high local stress, able to contain high pressure, without exceeding the yield stress of the assembled relief valve  500 . Namely, the flexible nature of O-ring materials accommodate imperfections in the mounting parts. Generally, the O-ring  503  can be designed to be seated in the O-ring seat  609  and compressed during assembly between the assembled relief valve  500  and the housing  607  of a cylinder, creating a seal at the interface. It is noted that O-rings can be one of the most common seals used in machine design because they are inexpensive and easy to make, reliable, and have simple mounting requirements, however, there can be variations in profile design other than circular. 
         [0037]    The soldering, welding or brazing can be used as exemplary methods for the engaging washers  603  on the receiving parts  605  of the cylinder. Soldering can be performed in a number of ways, for example, including passing parts over a small fountain in a bulk container of molten solder (wave soldering), heating assemblies by use of an infrared lamp, or by using a point source such as an electric soldering iron, a brazing torch, or a hot-air soldering tool. 
         [0038]      FIG. 6B  is a flowchart of assembly of relief valve, in accordance with an embodiment of the present invention. In step  651 , a manufacturer (assembler) can determine whether to set a pressure relief level (predetermined pressure relief level). When the level is determined, per step  653 , the manufacturer can select proper members of relief valve core based on the desired pressure relief level. The members of the relief valve core includes a head, spring, a valve pin (valve pin) or a gasket. In step  655 , the relief valve core member can be disposed within the valve body which has a seat to receive the relief valve core member and passageway openings. Unlike the conventional threaded engaging method, in step  657 , the relief valve core members can be engaged with the valve body using a spinning process as shown in the  FIG. 5 . A tester can test whether the engaged relief valve can conform to the regulation in step  659 . If the relief valve passes a certain requirements, the engaged relief valve can be disposed within a seat formed in the housing of a cylinder. The O-ring is positioned on the O-ring seat to receive and to seal spaces between the engaged relief valve and the housing of the cylinder. Per step  663 , the housing is sealed off with a washer using soldering or brazing. 
         [0039]    While the invention has been described in connection with a number of embodiments and implementations, the invention is not so limited but covers various obvious modifications and equivalent arrangements, which fall within the purview of the appended claims. Although features of the invention are expressed in certain combinations among the claims, it is contemplated that these features can be arranged in any combination and order.