Patent Publication Number: US-2022213968-A1

Title: Welded check valve

Description:
FIELD 
     This disclosure is directed to check valves, particularly welded check valves. 
     BACKGROUND 
     Check valves allow flow of a fluid in only a single direction, obstructing flow in the opposite direction to that single direction of permitted flow. 
     Check valves typically are assembled by arranging the internal components and screwing together the pieces that form the outer body of the check valve. Machining of the screws can be costly, and temperature variations can lead to media leakage at the screwed joint of the check valve. 
     SUMMARY 
     This disclosure is directed to check valves, particularly polymeric components welded together to create check valves. Welding the polymeric components of check-valves together simplifies manufacture of check valve components while producing a higher quality seal. Additionally, the elimination of threaded connections reduces potential particle generation caused during assembly of threaded components. Thus, welded check valves may offer improved performance in high-purity such as controlling fluid flows during semiconductor manufacture. Check valves may be welded using thermal welding techniques. Such thermal welding may be enabled by the inclusion of retaining features that allow polymeric check valve components to be held away from the site of the weld or the seam. Holding the check valve components away from the weld site can prevent the welding process from damaging or improperly bonding melt processable components of the check valve. 
     A check valve embodiment includes an internal passage, and is configured to control a fluid flow through the internal passage. The check valve includes an internal assembly. The internal assembly has a poppet assembly, a spring, contacting the poppet assembly at a first end, a disc including one or more through holes, the disc contacting the spring, a first outer piece having a first aperture and an opening opposite the first aperture, a second outer piece having a second aperture and a second opening opposite the second aperture. The second outer piece is joined to the first outer piece by a weld at the opening opposite the second aperture. The first outer piece and the second outer piece define an internal space for retaining the internal assembly. A disc retaining feature is located within the internal space, the retaining feature configured to selectively retain the disc in a position within the first outer piece away from the weld. This feature advantageously retains the internal components of the check valve away potentially damaging heat during the welding process. The internal assembly is configured to obstruct a fluid flow through the internal passage in one direction and permit flow through the internal passage in an opposite direction. 
     In an embodiment, the check valve includes a poppet assembly retaining feature. The poppet assembly retaining feature includes a plurality of retaining ribs extending from the first outer piece into the internal space, wherein the retaining ribs of the first plurality of retaining ribs are separated from one another by a first plurality of gaps, and each of the plurality of gaps is larger than a thickness of an outermost edge of the poppet assembly. 
     In an embodiment, the outermost edge of the poppet assembly defines a diameter that is smaller than a diameter of the internal space and larger than a distance between opposing retaining features of the plurality of retaining ribs. 
     In an embodiment, the poppet assembly includes a poppet and a poppet assembly disc, the poppet assembly disc includes one or more through holes, and the poppet assembly disc includes the outer edge of the poppet assembly. 
     In an embodiment, the plurality of retaining ribs is an even number of the retaining ribs and the plurality of gaps is an even number of the gaps. 
     In an embodiment, the disc retaining feature includes a plurality of retaining ribs extending from the first outer piece into the internal space. The retaining ribs of the second plurality of retaining ribs are separated from one another by a second plurality of gaps, and each of the second plurality of gaps is longer than a thickness of the outermost edge of the poppet assembly and a thickness of the disc. 
     In an embodiment, the disc retaining feature includes one or more detents formed on an inner surface of the first outer piece. In an embodiment, the detents do not allow the disc to pass when an outer surface of the first outer piece is compressed and allow the disc to pass when the outer surface of the first outer piece is not compressed. 
     In an embodiment, the first outer piece includes an annular groove formed on an inner surface of the first outer piece. In an embodiment, the disc retaining feature is a snap ring configured to be inserted into the annular groove, wherein when the snap ring is inserted into the annular groove, the snap ring has an interior diameter that is smaller than an outer diameter of the disc. In an embodiment, the disc is configured to be inserted into the annular groove and the annular groove is the retaining feature. 
     In an embodiment, the first outer piece, second outer piece, poppet assembly, and spring each comprise one or more fluoropolymers. The fluoropolymers may be melt processable. 
     In an embodiment, a method of assembling a check valve includes inserting a poppet assembly into a first outer piece of the check valve, the first outer piece including an inlet of the check valve, placing a spring against the poppet assembly, inserting a disc, such that the disc contacts the spring, and welding the first outer piece to a second outer piece at a weld joint. The disc is retained in a position away from the weld joint during the welding by one or more features of the first outer piece of the check valve. 
     In an embodiment, the disc is retained by a retaining feature including a plurality of retaining ribs on an inner surface of the first outer piece, wherein during the inserting of the disc, the disc is rotated such that the outer edges of the disc pass through gaps between ribs of the plurality of retaining ribs, and the method further comprises rotating the disc such that the disc contacts the plurality of retaining ribs. 
     In an embodiment, during the inserting of the poppet assembly, the poppet assembly is rotated such that the outer edges of the poppet assembly pass through gaps between ribs of the plurality of retaining ribs. 
     In an embodiment, during the inserting of the poppet assembly, the poppet assembly passes a second retaining feature, the second retaining feature comprising a plurality of second retaining ribs, and the method further includes rotating the poppet assembly such that when the poppet assembly moves along the axis of the first outer piece away from the inlet of the check valve, the poppet assembly is capable of contacting the plurality of second retaining ribs. 
     In an embodiment, the method further includes moving the disc such that it is retained by a plurality of retaining ribs proximal to the weld, after the welding of the first outer piece to the second outer piece. 
     In an embodiment, welding the first outer piece to the second outer piece includes thermal welding. 
     In an embodiment, the thermal welding includes heating a welding surface of the first outer piece using a first side of a heating paddle, heating a welding surface of the second outer piece using a second side of the heating paddle, and pressing the welding surface of the first outer piece and the welding surface of the second outer piece together. 
     In an embodiment, the method further includes testing flow through the first outer piece in a first direction and testing flow through the first outer piece in a second direction, opposite the first, after inserting the disc and prior to the welding. 
    
    
     
       DRAWINGS 
         FIG. 1  shows an exploded view of a check valve according to an embodiment. 
         FIG. 2  shows a sectional view of a check valve according to an embodiment. 
         FIGS. 3A-3H  show the steps of an example of inserting a poppet, spring and disc into a check valve according to an embodiment. 
         FIG. 4  shows a flow chart of a method according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     This disclosure is directed to check valves, particularly welded check valves. 
       FIG. 1  shows an exploded view of a welded check valve according to an embodiment. Welded check valve  100  includes first outer piece  102 , poppet assembly  104 , spring  106 , disc  108 , and second outer piece  110 . First outer piece  102  includes an aperture  112  and an opening  114 . Second outer piece  110  includes aperture  116  and opening  118 . When assembled, opening  114  of first outer piece  102  is welded to the opening  118  of second outer piece  110 . 
     First outer piece  102  defines part of the body of check valve  100 . First outer piece  102  includes an aperture  112 . In the embodiment shown in  FIG. 1 , aperture  112  forms an inlet of the check valve  100  and is part of an internal channel through the check valve  100 . First outer piece  102  includes opening  114 . An inner surface of first outer piece  102  may include retaining features (not shown) to position or restrict movement of one or more of poppet assembly  104  or disc  108 . 
     Poppet assembly  104  is configured to fit within first outer piece  104 . Poppet assembly  104  includes a poppet  120  and a poppet assembly disc  122 . 
     In poppet assembly  104 , the poppet  120  is configured to obstruct flow through the aperture  112  when the poppet  120  is positioned against it, for example by force from spring  106  or pressure provided by flow through check valve  100  towards aperture  112 . The poppet  120  is configured to be pushed away when a flow entering through aperture  112  provides more force than that provided by spring  106 . The poppet is configured to allow flow in one direction, from aperture  112  towards opening  118  of the, and block flow in the opposite direction. 
     In poppet assembly  104 , poppet assembly disc  122  is a circular disc having a diameter such that it can fit inside first outer piece  102 . Poppet assembly disc  122  may have a diameter that allows poppet assembly  104  to be retained by one or more retaining features within first outer piece  102 . Poppet assembly disc  122  includes one or more through holes allowing fluid to pass through. Poppet assembly disc may be configured such that the travel of the poppet assembly  104  is restricted by one or more retaining features provided on an inner surface of first outer piece  102 . 
     In an embodiment, poppet assembly  104  is formed integrally, with the poppet assembly disc being an extension from the poppet. In an embodiment, poppet assembly  104  includes a poppet assembly disc that is separate component from the poppet, and the poppet and poppet assembly disc are fixed to one another, for example via a mechanical interface, an adhesive, or any suitable methods of joining or combinations thereof. 
     Spring  106  may be a spring configured to contact poppet assembly  104  and disc  108 . Spring  106  is configured such that it is compressed between poppet assembly  104  and disc  108 . Spring  106  presses poppet assembly  104  against aperture  112  when unopposed by a force acting on poppet assembly  104 . The force with which spring  106  presses poppet assembly  104  may be a small force that is readily overcome by the pressure of flow through aperture  112 . It is understood that a person having ordinary skill in the art can select an appropriate spring force for operation of the check valve. In an embodiment, spring  106  may be selected such that a flow from aperture  112  providing less than approximately 1 psi of pressure may cause spring  106  to be compressed and poppet assembly  104  moved to allow flow through the check valve  102 . Spring  106  may be a molded polymer spring. 
     Disc  108  is used to retain spring  106  and position spring  106  such that spring  106  presses the poppet assembly  104 . Disc  108  includes one or more through holes allowing fluid to pass through disc  108 . Disc  108  is configured to fit within first outer portion  102 . In an embodiment, disc  108  is configured to be retained by a retaining feature located within first outer portion  102 . In an embodiment, disc  108  has an outer diameter that is smaller than the diameter within first outer portion  102 , but larger than a distance between two opposing points on one or more retaining features within first outer portion  102 . 
     Second outer piece  110  combined with first outer piece  102  form the body of check valve  100 . Second outer piece  110  includes aperture  116  and opening  118 . In an embodiment, aperture  116  is an outlet of the check valve. Opening  118  is at an end of the second outer piece opposite the aperture  116 . Opening  118  may be surrounded by a welding surface. 
     When assembled, opening  114  of first outer piece  102  is welded to the opening  118  of second outer piece  110 . Prior to welding, ends  114  and  118  may each include a flat welding surface, and the welding surfaces may have corresponding sizes and shapes. In an embodiment, welding surfaces at the ends  114  and  118  match one another such that they completely contact one another. The weld may be, for example, a thermal weld. The weld may be formed by gripping each of first outer piece  102  and second outer piece  104 , for example via a clamp or a vise, heating each of ends  114  and  118 , for example using a heated paddle, aligning the ends  114  and  118  with one another, and pressing together the heated ends  114  and  118 . In an embodiment, following the welding of ends  114  and  118 , disc  108  may be released from one set of retaining features within first outer piece  102 . An example of a thermal welding process is disclosed in U.S. Pat. No. 4,929,293, herein incorporated by reference in its entirety. 
     In an embodiment, all components of the check valve  100  may be made of polymer materials. In an embodiment, all components of check valve  100  are made of the same polymer material. In an embodiment, at least some of the components of check valve  100  may be made of different fluoropolymers from one another. In an embodiment, the polymer material is a fluoropolymer. Examples of fluoropolymers used to form the components may include, but are not limited to, fluoropolymers such as perfluoroalkoxy alkane polymer (PFA), ethylene and tetrafluoroethylene polymer (ETFE), ethylene, tetrafluoroethylene and hexafluoropropylene polymer (EFEP), polychlorotrifluoroethylene (PCTFE) and fluorinated ethylene propylene polymer (FEP), all of which are melt-processable. In addition to providing a non-corrosive and inert construction, many fluoropolymers, such as PFA, are injection moldable and extrudable. In one preferred embodiment, the fluoropolymer is perfluoroalkoxy alkane polymer (PFA). In other embodiments, the fluoropolymer can be polytetrafluoroethylene (PTFE) or tetrafluoroethylene polymer (PTFE) or modified tetrafluoroethylene polymer (TFM), which are not melt-processable, but can be compression molded and machined. 
       FIG. 2  shows a sectional view of a check valve  200  according to an embodiment. In the embodiment shown in  FIG. 2 , first outer piece  202  is joined to second outer piece  204  at weld  206 . First outer piece  202  and second outer piece  204  define an internal space containing poppet assembly  208 , spring  210 , and disc  212 . The internal surface of first outer piece  202  includes poppet assembly retaining features  214 , disc retaining features  216 , and welding disc retaining features  218 . 
     First outer piece  202  is part of the body of check valve  200 . First outer piece  202  includes an aperture  220  at one end, and an opening  222  at the opposite end. A welding surface may surround opening  222 . The first outer piece  202  has an internal space between aperture  220  and opening  222 . This internal space is part of an internal passage through the check valve  200 . The internal space is defined by an inner surface  224  of the first outer piece. 
     Second outer piece  204  is another part of the body of check valve  200 . Second outer piece  204  includes an aperture  226  at one end and an opening  234  at the opposite end. 
     Weld  206  joins first outer piece  202  and second outer piece  204  such that they define an internal space. The internal space contains an internal assembly including poppet assembly  208 , spring  210 , and disc  212 . The weld may be any suitable weld joining first outer piece  202  and second outer piece  204 . Suitable welds may include, for example, a thermal weld or an ultrasonic weld. In an embodiment, weld  206  is a thermal weld. 
     Poppet assembly  208  may include poppet  228  and poppet assembly disc  230 . In an embodiment, poppet  228  and poppet assembly disc  230  are separate components joined to one another, for example by one or more of mechanical interface, adhesives, or any other suitable method of fixing parts to one another. 
     In the embodiment shown in  FIG. 2 , poppet  228  may include a lip  232  extending from the outer perimeter of the poppet  228  towards aperture  220 . The lip  232  may form a sealing surface when poppet  228  is prohibiting flow towards that aperture  220 . The lip  232  may be flexible to form the sealing surface. The lip  232  may be configured to interface with an internal surface of first outer piece  202  to form a seal preventing the flow of fluid past the poppet  228  towards the aperture  220 . The poppet  228  may have a diameter that exceeds the diameter of a channel to the aperture  220  towards which poppet  228  restricts flow. When flow is coming from aperture  220  and directed towards aperture  226 , the flow may apply pressure to the poppet such that the poppet assembly moves towards aperture  226 , compressing spring  210 . This positions the poppet assembly such that flow from aperture  220  may pass poppet  228 . The flow then passes through the through holes formed in poppet assembly disc  230  and disc  212 , passing through the internal space within check valve  200  to aperture  226 . 
     Poppet assembly disc  230  is a circular disc having a diameter such that it can fit inside first outer piece  202 . Poppet assembly disc  230  may have a diameter that allows poppet assembly  208  to be retained by one or more poppet assembly retaining features  214  when in an operational position. Poppet assembly disc  230  includes one or more through holes allowing fluid to pass through. Poppet assembly disc  230  may be configured such that poppet assembly  208  may travel in a direction towards or away from aperture  226  with respect to aperture  220 . The direction of travel of poppet assembly  208  may be in a direction of flow of fluid through the internal space of check valve  200  at the poppet assembly  208 . The travel of poppet assembly  208  may be restricted by one or more poppet assembly retaining features  214  provided on an inner surface  224  of first outer piece  202 . 
     Spring  210  is a spring configured to contact poppet assembly  208  and disc  212 . Spring  210  is configured such that it presses poppet assembly  208  to obstruct aperture  220  when unopposed. The force with which spring  210  presses poppet assembly  208  may be a small force that is readily overcome by the pressure of flow through aperture  220 . Spring  210  may be a molded polymer spring. 
     Disc  212  secures spring  210  such that spring  210  can apply force to poppet assembly  208 . Disc  212  is held in position by disc retaining features  216 . Disc  212  includes one or more through holes configured to allow fluid to pass through disc  212 . In an embodiment, disc  212  is configured to be retained by disc retaining features  216 . In an embodiment, disc  212  has an outer diameter that is smaller than the diameter of the internal space within first outer portion  202 , but larger than a distance between two points of the disc retaining features  216  opposing one another with respect to a center line of the internal space within first outer piece  202 . 
     The inner surface  224  of first outer piece  202  includes poppet assembly retaining features  214 . In the embodiment shown in  FIG. 2 , the poppet assembly retaining features are formed integrally with the inner surface  224  of first outer piece  202  and extend inwardly from that surface. In this embodiment, the poppet assembly retaining features may be two or more ribs, the ribs separated by two or more gaps between them. The ribs may project inwards such that the distance between points on the ribs that oppose one another with respect to a center of the internal space within first outer piece  202  is smaller than an outer diameter of the poppet assembly disc  230 . In an embodiment, the poppet assembly retaining features  214  may be a snap ring or included on a snap ring that is inserted into a groove formed on inner surface  224  of first outer piece  202 . Poppet assembly retaining features  214  may be closer to the aperture  220  and further from aperture  226  of the first outer piece  202  than other retaining features such as disc retaining features  216  or welding disc retaining feature  218 . 
     In the embodiment shown in  FIG. 2 , disc retaining features  216  are included in inner surface  224  of first outer piece  220 . The disc retaining features  216  may be formed integrally with first outer piece  202 . In this embodiment, the disc retaining features may be two or more ribs, the ribs separated by two or more gaps between them. The ribs may project inwards such that the distance between points on the ribs that oppose one another with respect to a center of the internal space within first outer piece  202  is smaller than an outer diameter of the disc  212 . In an embodiment, the disc retaining features  216  may be a snap ring or included on a snap ring that is inserted into a groove formed on inner surface  224  of first outer piece  202 . Disc retaining features  216  may be closer to the aperture  226  and further from aperture  220  of the first outer piece  202  than other retaining features such as poppet assembly retaining features  214  or welding disc retaining feature  218 . 
       FIG. 2  shows optional welding disc retaining feature  218 . In the embodiment shown in  FIG. 2 , welding disc retaining feature  218  is an annular ridge projecting from the inner surface  224  of first outer piece  202 , located between the poppet assembly retaining features  214  and the disc retaining features  216  along the length of the first outer piece  202 . In an embodiment, welding disc retaining feature  218  is a detent. In an embodiment, welding disc retaining feature  218  is sized to provide an interference fit, such that the disc  212  may be pushed past the welding disc retaining feature  218  when force is applied to disc  212 . In this embodiment, when no outside force is applied to disc  212  beyond spring  210 , the interference fit does not allow disc  212  to pass the welding disc retaining feature  218 . In an embodiment, welding disc retaining feature  218  is sized such that disc  212  may pass the welding disc retaining feature  218  when no pressure is applied to an exterior of first outer piece  202 , but that when pressure is applied to the exterior of the first outer piece  202 , welding disc retaining feature  218  provides sufficient friction to hold disc  212  in place or prohibit the passage of disc  212  towards the opening  222 . Welding disc retaining feature  218  may be used to secure disc  212  at a position further from the weld during the weld, then release the disc  212  and allow the disc  212  to move to disc retaining features  216  once the check valve  200  is assembled and ready for use. 
     The internal assembly including poppet assembly  208 , spring  210 , and disc  212  is configured to obstruct a fluid flow through the internal passage in one direction and permit flow through the internal passage in an opposite direction. In an embodiment, when fluid is flowing from aperture  220  of the first outer piece  202  towards aperture  226  of the second outer piece  204 , the fluid flow applies pressure overcoming the spring force provided by spring  210 , causing poppet assembly  208  to move away from aperture  220  and towards aperture  226 . This positions poppet  228  such that it does not obstruct flow from aperture  220 , and flow passes poppet  228  and through the through holes formed in poppet assembly disc  230  and disc  212  to aperture  226 . When flow is in the opposite direction, from aperture  226  towards aperture  220 , spring  210  acts on poppet assembly  208  and positions the poppet  228  such that it obstructs flow to aperture  220 . The pressure of the flow from aperture  226  towards aperture  220  also presses on poppet  228 , sealing it in position and prohibiting flow to aperture  220 . The embodiment shown in  FIG. 2  thus provides flow in only one direction through the internal space within check valve  200 , and obstructs flow in the opposite direction. 
     In an embodiment, all components of the check valve  200  may be made of polymer materials. In an embodiment, all components of check valve  200  are made of the same polymer material. In an embodiment, at least some of the components of check valve  200  may be made of different fluoropolymers from one another. In an embodiment, the polymer material is a fluoropolymer. Examples of fluoropolymers used to form the components may include, but are not limited to, fluoropolymers such as perfluoroalkoxy alkane polymer (PFA), ethylene and tetrafluoroethylene polymer (ETFE), ethylene, tetrafluoroethylene and hexafluoropropylene polymer (EFEP), polychlorotrifluoroethylene (PCTFE) and fluorinated ethylene propylene polymer (FEP), all of which are melt-processable. In addition to providing a non-corrosive and inert construction, many fluoropolymers, such as PFA, are injection moldable and extrudable. In one preferred embodiment, the fluoropolymer is perfluoroalkoxy alkane polymer (PFA). In other embodiments, the fluoropolymer can be polytetrafluoroethylene (PTFE) or tetrafluoroethylene polymer (PTFE) or modified tetrafluoroethylene polymer (TFM), which are not melt-processable, but can be compression molded and machined. 
       FIGS. 3A-3H  show the steps of an example of inserting a poppet assembly  302 , spring  304  and disc  306  into a first outer piece  300  of a check valve according to an embodiment. 
       FIG. 3A  shows the first outer piece  300  of the check valve that is provided in a method of assembling a valve according to an embodiment. Poppet assembly retaining features  308 , disc retaining features  310 , and welding disc retaining feature  312  can be seen within first outer piece  300 . 
     Poppet assembly retaining features  308  include a plurality of ribs located towards the aperture formed in first outer piece  300  and further from the open end in the embodiment shown in  FIG. 3A . The plurality of ribs include a plurality of gaps extending inwards from an inner surface of first outer piece  300 . In an embodiment, the poppet assembly retaining features  308  may be at least two ribs, with at least two gaps formed between the at least two ribs. The ribs may be formed integrally with first outer piece  300 . Each of the plurality of gaps is sized such that the poppet assembly  302  may pass the poppet assembly retaining features  308  when the poppet assembly  302  is rotated with respect to its operation position. In an embodiment, the ribs may be included on a snap ring inserted into a groove formed in first outer piece  300 . In an embodiment, the poppet assembly retaining features  308  are replaced by a groove configured to accept a snap ring, the inner diameter of the snap ring being smaller than an inner diameter of the internal space within first outer piece  300 . 
     Disc retaining features  310  include a plurality of ribs located towards the open end and further from the aperture formed in first outer piece  300  in the embodiment shown in  FIG. 3A . The plurality of ribs are separated by a plurality of gaps extending inwards from an inner surface of first outer piece  300 . In an embodiment, the disc retaining features  310  may be at least two ribs, with at least two gaps formed between the at least two ribs. Each of the plurality of gaps is sized such that the poppet assembly  302  and the disc  306  may each pass the disc retaining features  310  when the poppet assembly  302  or disc  306  are rotated with respect to their operational positions. The ribs may be formed integrally with first outer piece  300 . In an embodiment, the ribs may be included on a snap ring inserted into a groove formed in first outer piece  300 . In an embodiment, the disc retaining features  310  are replaced by a groove configured to accept a snap ring, the inner diameter of the snap ring being smaller than an inner diameter of the internal space within first outer piece  300 . 
     The embodiment shown in  FIG. 3A  further includes optional welding disc retaining feature  312 . In the embodiment shown in  FIG. 3A , the welding disc retaining feature  312  is a small projection from the inner surface of first outer piece  300 , located between the poppet assembly retaining features  308  and the disc retaining features  310 . Welding disc retaining feature  312  is sized such that disc  308  may pass the welding disc retaining feature  312  when no pressure is applied to an exterior of first outer piece  300 , but that when pressure is applied to the exterior of the first outer piece  300 , welding disc retaining feature  312  provides sufficient friction to hold disc  308  in place or prohibit the passage of disc  308  towards the open end of first outer piece  300 . Welding disc retaining feature  312  may be used to secure disc  308  at a position further from the weld during the weld, then allow the disc  308  to advance to disc retaining features  310  once the check valve is assembled and ready for use. The position of the disc when held by welding disc retaining feature  312  may be seen in  FIG. 3H . 
       FIG. 3B  shows insertion of a poppet assembly  302  into the first outer piece  300 . The poppet assembly is rotated such that the poppet assembly disc may pass through gaps between the disc retaining features  310  and through gaps between the poppet assembly retaining features  308 . The poppet assembly thus can be positioned opposite the open end of first outer piece  300  towards the aperture formed in first outer piece  300 . 
       FIGS. 3C and 3D  show rotation of the poppet assembly  302  into an operating position. The poppet assembly  302  is in the process of being rotated in  FIG. 3C , and fully rotated in  FIG. 3D . The poppet assembly in  FIG. 3D  is in the operational positon, where the plane of the disc included in poppet assembly  302  perpendicular to the direction fluid would enter through the aperture formed in first outer piece  300 . In the operational position, poppet assembly  302  may be slidable between a closed position where the poppet covers the fluid path to an aperture of the first outer piece  300  and a fully open position where the poppet assembly contacts the poppet assembly retaining features  308 . 
     In an embodiment where the poppet assembly retaining features  308  include or are a snap ring, poppet assembly  302  may be placed into first outer piece  300  in the operating position shown in  FIG. 3D  without rotation as shown in  FIGS. 3B and 3C , and the snap ring subsequently inserted into first outer piece  300  and snapped into the groove. 
       FIG. 3E  shows placement of the spring into contact with the poppet assembly. The spring is directly inserted into the first outer piece  300  and an end of the spring  304  contacts the poppet assembly  302 . 
       FIG. 3F  shows insertion of the disc  306  into the check valve. The insertion of disc  306  shown in  FIG. 3F  is performed while spring  304  is in position contacting poppet assembly  302 . The disc is rotated such that the outermost edges of the disc can pass through the gaps in the disc retaining features  310  during insertion. 
       FIG. 3G  shows the disc  306  in an operational position, retained by the disc retaining features  310 . The disc is rotated such that the outermost edges of the disc  306  can contact the disc retaining features  310 . In the operational position, spring  304  presses disc  306  against the disc retaining features  310 , such that the disc  306  is positioned against the disc retaining features  310  and spring  304  can apply force against poppet assembly  302 . 
     In an embodiment where the disc retaining features  310  are or include a snap ring, disc  306  may be placed against spring  304  in the operational position shown in  FIG. 3 , then the snap ring inserted into a groove at the position of the disc retaining features  310 . 
       FIG. 3H  shows the disc  306  moved to an optional position for welding, further from the welding surface on the end of the first outer piece  300 . The first outer piece  300  and the components retained therein may then be welded to a second outer piece (not shown) to form a check valve. To achieve the position of the disc  306  shown in  FIG. 3H , the disc  306  in the operational position shown in  FIG. 3G  is pressed towards the poppet assembly  304  and held in that position with the spring compressed. The optional welding disc retaining feature  312  may provide an interference fit with disc  306 . In an embodiment, the disc  306  may be pressed past the optional welding disc retaining feature  312  by application of force on disc  306 . In an embodiment, the interference fit of retaining feature  312  may retain disc  306  when disc  306  is not subject to force outside of that provided by spring  304 . In an embodiment, the interference fit of optional welding disc retaining feature  312  and disc  306  may be affected by external force on first outer piece  300 . In this embodiment, while the disc  306  is in this position, the first outer piece  300  may have pressure applied to an exterior surface, for example via a clamp such as a clamp used to secure the piece for welding. The disc  306  may then be released while the pressure is applied to the external surface, with spring  304  applying force that moves disc  306  to the welding disc retaining feature  312 , where friction or mechanical interference retains disc  306  while the pressure is applied to the external surface. Once the pressure is removed, disc  306  may be able to pass welding disc retaining feature  312  and be retained instead by disc retaining features  310 . 
       FIG. 4  shows a flow chart of a method  400  according to an embodiment. Method  400  includes inserting a poppet assembly into a first outer piece of the check valve  402 , placing a spring against the poppet assembly  404 , and inserting a disc  406 . Optionally, method  400  includes moving the disc such that it is retained further from the weld  408  than an operating position of the disc. Method  400  further includes welding the first outer piece to a second outer piece at a weld joint  410 . In an embodiment, method  400  optionally includes testing flow through the first outer piece in a first direction  412  and testing flow through the first outer piece in a second direction, opposite the first  414 , after inserting the disc and prior to the welding. 
     Inserting a poppet assembly into a first outer piece of the check valve  402  includes placing the poppet assembly into the first outer piece. In an embodiment, the poppet assembly may be rotated such that the outermost edge of the poppet assembly may pass poppet assembly retaining features, such as by passing through gaps between ribs included in the poppet assembly retaining features. In this embodiment, the poppet assembly may further pass disc retaining features in the same manner. In this embodiment, the poppet assembly may then be rotated into an operational position prior to placing the spring against the poppet assembly  404 . The operational position may include a plane of the disc of the poppet assembly being perpendicular to a direction of flow through the check valve. In an embodiment, the poppet assembly may be oriented in the operational position when inserted, and a snap ring inserted into a groove to retain the poppet assembly during use prior to placing the spring against the poppet assembly  404 . 
     A spring is placed against the poppet assembly  404 . An end of the spring may be configured to engage a feature on the poppet assembly. The spring may be inserted into the first outer piece via the open end of the first outer piece. The spring also contacts a disc that is subsequently inserted  406 . 
     A disc is inserted  406 . The disc inserted at  406  contacts the spring inserted at  404 . In an embodiment, inserting the disc  406  includes rotating the disc such that the outermost edge of the disc may pass disc retaining features, such as by passing through gaps between ribs included in the disc retaining features. In this embodiment, the disc may be rotated into an operational position where the disc is held by the disc retaining features. In an embodiment where the disc retaining features include or are a snap ring, the disc may be inserted in the operational position and held within the first outer piece, and the snap ring may then be inserted and positioned within a groove, such that when the snap ring is in the groove and the disc released, the disc retaining features contact the disc. 
     Optionally, method  400  includes moving the disc such that it is retained further from the weld  408  than an operating position of the disc. In this optional step, the disc may be moved towards the poppet assembly and pass a welding disc retaining feature. The disc is held in that position while a pressure is applied. In an embodiment, the pressure is applied via a clamp that holds the first outer portion of the check valve during the welding  410 . The pressure causes the welding disc retaining feature to be in position to apply friction or mechanical interference retaining the disc at a position further from the welding point than the disc retaining features are. 
     Method  400  includes welding the first outer piece to a second outer piece at a weld joint  410  to form a check valve. The weld may be a thermal weld. The thermal weld may be a thermal welding technique suitable for joining polymer materials such as, for example, fluoropolymers. In an embodiment, the thermal weld may be performed by heating the welding surfaces surrounding the openings at the ends of the first outer piece and the second outer piece, positioning the heated welding surfaces opposite one another, and pressing the welding surfaces against one another to form the weld. In an embodiment, the welding surfaces are heated on opposing sides of a heated paddle prior to performing the welding. The temperature to which the welding surfaces are heated may be a suitable welding temperature for the material or materials used at the welding surfaces. The welding of the first outer piece to the second outer piece  410  defines an internal space within the welded first and second outer pieces, which contains an internal assembly including the poppet assembly, the spring, and the disc. In an embodiment, the welding of the first outer piece to the second outer piece includes heating the welding surfaces to a temperature at or above the melting point of the material at the welding surfaces. In an embodiment, the temperature provided to the welding surfaces may be between 1250° F. and 2000° F. In an embodiment, welding the first outer piece to the second outer piece may be automated, with a machine holding the assembled first outer piece and the second outer piece, heating the welding surfaces with the paddle for a predetermined period of time, removing the paddle, and pressing the welding surfaces together. 
     In an embodiment, method  400  optionally includes testing flow through the first outer piece in a first direction  412  and testing flow through the first outer piece in a second direction, opposite the first  414 , after inserting the disc  406  and prior to the welding  410 . The first direction may be a direction from an aperture included in the first outer piece towards an opening at an opposite end of that first outer piece. The testing of flow in the first direction may be tested  412  by providing such a flow in the first direction. The check valve is functional when it permits flow in the first direction to pass through the poppet assembly, spring, and disc. The testing of flow in the second direction  414  may be tested by providing a flow in the opposite direction. The check valve 
     Aspects: 
     It is understood that any of aspects 1-X can be combined with any of aspects Y-Z. 
     Aspect 1. A check valve including an internal passage, the check valve configured to control a fluid flow through the internal passage, the check valve comprising:
         (a) an internal assembly having,
           (i) a poppet assembly;   (ii) a spring, contacting the poppet assembly at a first end; and   (iii) a disc including one or more through holes, the disc contacting the spring;   
           (b) a first outer piece having a first aperture and first opening opposite the first aperture;   (c) a second outer piece having a second aperture and a second opening opposite the second aperture, wherein the first outer piece and the second outer piece are connected by a weld at the first opening and the second opening to define an internal space for retaining the internal assembly; and   (d) a disc retaining feature located within the internal space, the retaining feature configured to selectively retain the disc in a position within the internal space away from the weld,
 
wherein the internal assembly is configured to obstruct a fluid flow through the internal passage in one direction and permit flow through the internal passage in an opposite direction.
       

     Aspect 2. The check valve according to aspect 1, comprising a poppet assembly retaining feature, wherein the poppet assembly retaining feature comprises: 
     a plurality of retaining ribs extending from the first outer piece into the internal space, wherein the retaining ribs of the first plurality of retaining ribs are separated from one another by a first plurality of gaps, and
 
each of the plurality of gaps is larger than a thickness of an outermost edge of the poppet assembly.
 
     Aspect 3. The check valve according to aspect 2, wherein the outermost edge of the poppet assembly defines a diameter that is smaller than a diameter of the internal space and larger than a distance between opposing retaining features of the plurality of retaining ribs. 
     Aspect 4. The check valve according to any of aspects 2-3, wherein the poppet assembly comprises a poppet and a poppet assembly disc, the poppet assembly disc includes one or more through holes, and the poppet assembly disc includes the outer edge of the poppet assembly. 
     Aspect 5. The check valve according to any of aspects 2-4, wherein the plurality of retaining ribs is an even number of the retaining ribs and the plurality of gaps is an even number of the gaps. 
     Aspect 6. The check valve according to any of aspects 1-5, wherein the disc retaining feature comprises a plurality of retaining ribs extending from the first outer piece into the internal space, wherein the retaining ribs of the second plurality of retaining ribs are separated from one another by a second plurality of gaps, and each of the second plurality of gaps is longer than a thickness of the outermost edge of the poppet assembly and a thickness of the disc. 
     Aspect 7. The check valve according to any of aspects 1-6, wherein the disc retaining feature comprises one or more detents formed on an inner surface of the first outer piece. 
     Aspect 8. The check valve according to aspect 7, wherein the detents do not allow the disc to pass when an outer surface of the first outer piece is compressed and allow the disc to pass when the outer surface of the first outer piece is not compressed. 
     Aspect 9. The check valve according to any of aspects 1-8, wherein the first outer piece includes an annular groove formed on an inner surface of the first outer piece. 
     Aspect 10. The check valve according to aspect 9, wherein the disc retaining feature is a snap ring configured to be inserted into the annular groove, wherein when the snap ring is inserted into the annular groove, the snap ring has an interior diameter that is smaller than an outer diameter of the disc. 
     Aspect 11. The check valve according to aspect 9, wherein the disc is configured to be inserted into the annular groove and the annular groove is the retaining feature. 
     Aspect 12. The check valve according to any of aspects 1-11, wherein the first outer piece, second outer piece, poppet assembly, and spring each comprise one or more fluoropolymers. 
     Aspect 13. A method of assembling a check valve, comprising:
         inserting a poppet assembly into a first outer piece of the check valve, the first outer piece including an inlet of the check valve;   placing a spring against the poppet assembly;   inserting a disc, such that the disc contacts the spring; and   welding the first outer piece to a second outer piece at a weld joint,   wherein the disc is retained in a position away from the weld joint during the welding by one or more features of the first outer piece of the check valve.       

     Aspect 14. The method according to aspect 13, wherein the disc is retained by a retaining feature including a plurality of retaining ribs on an inner surface of the first outer piece, wherein during the inserting of the disc, the disc is rotated such that the outer edges of the disc pass through gaps between ribs of the plurality of retaining ribs, and the method further comprises rotating the disc such that the disc contacts the plurality of retaining ribs. 
     Aspect 15. The method according to aspect 14, wherein during the inserting of the poppet assembly, the poppet assembly is rotated such that the outer edges of the poppet assembly pass through gaps between ribs of the plurality of retaining ribs. 
     Aspect 16. The method according to aspect 15, wherein during the inserting of the poppet assembly, the poppet assembly passes a second retaining feature, the second retaining feature comprising a plurality of second retaining ribs, and the method further includes rotating the poppet assembly such that when the poppet assembly moves along the axis of the first outer piece away from the inlet of the check valve, the poppet assembly is capable of contacting the plurality of second retaining ribs. 
     Aspect 17. The method according to any of aspects 13-16, further comprising moving the disc such that it is retained by a plurality of retaining ribs proximal to the weld, after the welding of the first outer piece to the second outer piece. 
     Aspect 18. The method according to any of aspects 13-17, wherein welding the first outer piece to the second outer piece comprises thermal welding. 
     Aspect 19. The method according to aspect 18, wherein the thermal welding comprises:
         heating a welding surface of the first outer piece using a first side of a heating paddle;   heating a welding surface of the second outer piece using a second side of the heating paddle; and   pressing the welding surface of the first outer piece and the welding surface of the second outer piece together.       

     Aspect 20. The method according to any of aspects 13-19, further comprising testing flow through the first outer piece in a first direction and testing flow through the first outer piece in a second direction, opposite the first, after inserting the disc and prior to the welding. 
     The examples disclosed in this application are to be considered in all respects as illustrative and not limitative. The scope of the invention is indicated by the appended claims rather than by the foregoing description; and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.