Patent Publication Number: US-2019178263-A1

Title: Constant tension snap-fit assembly

Description:
This application is a continuation of U.S. Nonprovisional application Ser. No. 14/813,964 filed Jul. 30, 2015, which is a bypass continuation application of International Application Nos. PCT/US2013/43288 and PCT/US2013/043294 filed May 30, 2013, which commonly claim the benefit of U.S. Provisional Application No. 61/760,022 filed Feb. 1, 2013, U.S. Provisional Application No. 61/760,023 filed Feb. 1, 2013, and U.S. Provisional Application No. 61/807,461 filed Apr. 2, 2013, all of which are incorporated by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     The present teachings generally include a jet pump assembly for draining a liquid trap. 
     BACKGROUND 
     The efficiency and functionality of a jet pump assembly is highly dependent upon the alignment of the jet pump nozzle with the diffuser at which the nozzle tip is directed. Plastic components can change their shape under different operating conditions. For example, plastic can swell in the presence of a medium such as automotive fuel, and then re-dry, shrinking to a smaller size. The relative fit of plastic components connected to one another can thus be dependent on the operating conditions. 
     SUMMARY 
     A jet pump assembly for draining a liquid trap is provided that includes a unitary nozzle carrier and a unitary venturi nozzle. The unitary nozzle carrier has a wall with an entrance port. The nozzle carrier has a longitudinal passage extending through the nozzle carrier and in fluid communication with the entrance port. The unitary venturi nozzle has an inlet and a nozzle tip forming an outlet. The nozzle carrier and the venturi nozzle are configured so that the venturi nozzle fits to the nozzle carrier in the longitudinal passage with the nozzle tip extending past the entrance port. The nozzle tip is in fluid communication with the entrance port. The alignment of a longitudinal axis of the venturi nozzle with a longitudinal axis of the nozzle carrier is thus dependent only on the fit of the carrier portion and the venturi nozzle when the venturi nozzle is fit to the carrier portion. 
     The above features and advantages and other features and advantages of the present teachings are readily apparent from the following detailed description of the best modes for carrying out the present teachings when taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration in cross-sectional view of a liquid trap assembly with a liquid trap and an integrated jet pump assembly, taken at the lines  1 - 1  in  FIG. 2 . 
         FIG. 2  is a schematic perspective illustration of the liquid trap assembly assembly of  FIG. 1 . 
         FIG. 3  is a schematic illustration in fragmentary cross-sectional view of the jet pump assembly supported in the liquid trap assembly of  FIG. 1 . 
         FIG. 4  is a schematic side view illustration of the jet pump assembly of  FIG. 1 . 
         FIG. 5  is a schematic illustration in cross-sectional view of the jet pump assembly in  FIG. 4  taken at lines  5 - 5  in  FIG. 4 . 
         FIG. 6  is a schematic cross-sectional illustration taken at lines  6  in  FIG. 4  of a venturi nozzle of the jet pump assembly of  FIG. 4  with the nozzle carrier removed. 
         FIG. 7  is a schematic cross-sectional illustration taken at lines  7  in  FIG. 4  of a nozzle carrier of the jet pump assembly of  FIG. 4  with the venturi nozzle removed. 
         FIG. 8  is a schematic illustration in cross-sectional view of an alternative jet pump assembly for use in the liquid trap assembly of  FIG. 1 . 
         FIG. 9  is a schematic illustration of the liquid trap assembly of  FIG. 1  mounted in a fuel tank and part of a vehicle fuel system. 
         FIG. 10  is a schematic illustration in end view of the liquid trap assembly of  FIG. 1 . 
         FIG. 11  is a schematic illustration in cross-sectional view of the liquid trap assembly taken at lines  11 - 11  in  FIG. 10  and showing a housing connected to an end cap. 
         FIG. 12  is a close-up fragmentary cross-sectional view of an extension of the housing trapped in a recess of the end cap under a first operating condition. 
         FIG. 13  is a close-up fragmentary cross-sectional view of the extension of the housing trapped in the recess of the end cap under a second operating condition. 
         FIG. 14  is a close-up fragmentary cross-sectional view of the extension of the housing trapped in the recess of the end cap under a third operating condition. 
         FIG. 15  is a close-up fragmentary cross-sectional view of an alternate extension for the housing shown trapped in the recess of the end cap under the first operating condition. 
         FIG. 16  is a close-up fragmentary cross-sectional view of the alternate extension of the housing trapped in the recess of the end cap under the second operating condition. 
         FIG. 17  is a close-up fragmentary cross-sectional view of the alternate extension of the housing trapped in the recess of the end cap under the third operating condition. 
         FIG. 18  is a schematic illustration in exploded perspective view of the liquid trap assembly of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to the drawings, wherein like reference numbers refer to like components throughout the several views,  FIG. 1  shows a liquid trap assembly  10  that efficiently drains liquid collected from vapor. The liquid trap assembly  10  can also be referred to as an active liquid drain. The liquid trap assembly  10  has a housing  12 . The housing  12  has a first port, referred to as a vapor flow inlet  14  (shown in  FIG. 2 ) and a second port, referred to as a vapor flow outlet  16  in fluid communication with an interior cavity  18  formed at least in part by the housing  12 . As shown in  FIG. 2 , the outlet  16  is formed by an upper cap  13  secured to the housing  12  with tabs  15  fit through tab retainers  17 . Vapor flows from the vapor flow inlet  14 , through the cavity  18 , to the vapor flow outlet  16 . Liquid entrained in the vapor flow is collected in a liquid trap  20  formed by the housing  12  at the bottom of the housing  12 . A filter  19  extends across the lowest portion of the trap  20 . The outlet  16  can be replaced by an outlet valve, or the housing  12  can have no outlet. 
     An end cap  23  is connected to the housing  12  in a manner described herein. The housing  12  can be a one-piece, molded plastic component. The end cap  23  can also be a one-piece, molded plastic component. Either or both of the housing  12  and an end cap  23  described can have features that promote separation of liquid and vapor, such as baffles and ribs. As used herein, the end cap  23  is referred to as a first component of the liquid trap assembly  10 , and the housing  12  is referred to as a second component of the liquid trap assembly  10 . 
     The liquid trap assembly  10  can be used in many applications. In one application described herein, the liquid trap assembly  10  is used in a fuel vapor recovery system  21  on a vehicle, shown schematically in  FIG. 9 . The vehicle can be a diesel, gasoline, or hybrid application. Vapor is vented from a fuel tank  22  that contains liquid fuel  93 . The vapor is vented through a vapor vent valve  26  that may provide pressure relief, rollover shutoff, and other functions. Vapor flows from the vapor vent valve  26  to the liquid trap assembly  10  through the inlet  14  and exits through the outlet  16  to a vapor recovery device, such as a canister (C)  28  filled with carbon granules. The canister  28  is periodically purged to an engine (E)  30 . The liquid trap assembly  10  is shown mounted within the fuel tank  22 . Alternatively, the liquid trap assembly  10  can be external to the fuel tank  22 . 
     Referring to  FIG. 1 , the housing  12  forms a first opening  35  in a sidewall adjacent to the liquid trap  20 . The opening  35  is selectively closed by a check valve  36 . Any type of valve can be used to close the opening  35 , or there can be no valve at the opening  35 . The check valve  36  includes a valve body  38  and a spring  40  that biases the valve body  38  into the first opening  35  to close the opening  35  and separate the cavity  18  and liquid trap  20  from a valve cavity  42  in which the spring  40  and valve body  38  are movable, as described herein. When the check valve  36  closes the opening  35 , it also prevents liquid from entering or exiting the liquid trap  20  through the opening  35 . The valve body  38  is generally annular and has a generally cone-shaped end that extends into the cavity  18 . The spring  40  has a diameter that fits inside the generally annular valve body  38 . A valve body with a different shape can also be used. For example, a ball valve may be used to close the opening  35 . 
     The liquid trap assembly  10  includes a jet pump assembly  44 . The jet pump assembly  44  includes a nozzle carrier  46  and a venturi nozzle  48 . The nozzle carrier  46  has an entrance port  50  that extends through a generally annular outer wall  55  of the nozzle carrier  46  in operative fluid communication with the liquid trap  20 , as best shown in  FIG. 1 . That is, a lower extent  53  of the cavity  42  is in communication with the entrance port  50 . When the valve  36  opens, the spring  40  depresses, and the valve body  38  will move past the lower extent  53  (to the left in  FIG. 1 ) so that the liquid trap  20  empties to the lower extent  53  and through the entrance port  50  into a longitudinal passage  52  (shown in  FIG. 3 ) of the nozzle carrier  46 . The longitudinal passage  52  extends completely through the nozzle carrier  46  as best shown in  FIGS. 3 and 7 , and is larger in the carrier portion  54  than in the diffuser portion  58 . The longitudinal passage  52  is in fluid communication with the entrance port  50 . The valve  36  is configured to prevent draining of the liquid trap  20  by the jet pump assembly  44  when a pressure differential created by liquid flow through the venturi nozzle  48  is below a predetermined level, and to allow fluid communication between the jet pump assembly  44  and the liquid trap  20  when the pressure differential is above the predetermined level. It should be appreciated, however, that the valve  36  is optional, and the jet pump assembly  44  could drain the liquid trap  20  sufficiently if no valve  36  was present. 
     Flow through the venturi nozzle  48  induces draining of the liquid trap  20 . As shown in  FIG. 9 , the jet pump assembly  44  is connected by tubing  90 ,  94  to a fuel pump  92  submerged in the liquid fuel  93 . The fuel pump  92  is also connected to the engine  30  via fuel discharge tubing  94 . Fuel is discharged from the fuel pump  92  at relatively high pressure through the fuel discharge tubing  94 . The tubing  90  branches from the fuel discharge tubing  94 , providing relatively high pressure liquid fuel flow to an inlet portion  63  of the housing  12  that is in fluid communication with an inlet  64  of the nozzle  48  indicated in  FIG. 3 . 
     Referring again to  FIG. 1 , fluid flowing out of the nozzle  48  creates a vacuum or at least a relatively low pressure area in the longitudinal passage  52  adjacent the entrance port  50 . Pressure is also reduced in the cavity  42  due to the vacuum or low pressure in the longitudinal passage  52 , creating a pressure differential across the valve body  36 , as pressure in the cavity  42  is lower than pressure in the cavity  18 . When the pressure differential reaches a predetermined level such that a force created by the pressure differential on the area of the valve body  38  exposed to the cavity  18  is greater than the force keeping the check valve  36  shut (in this case the force of the spring  40 ), the valve body  38  will move toward the end cap  23 , compressing the spring  40  and establishing fluid communication between the liquid trap  20  and the entrance port  50 . The jet pump assembly  44  is a fuel discharge assembly that has the propelling mechanism, due to the pressure differential and jet action through the nozzle  48 , to discharge liquid fuel in the trap  20  to the fuel tank  22 . 
     The jet pump assembly  44  utilizes high pressure fluid from the fuel pump  92  which flows through the nozzle  48  with a high velocity. The flow through the nozzle  48  is referred to as the primary flow or primary stream. The high velocity fluid leaving the nozzle  48  creates a low pressure or a vacuum in the area adjacent the nozzle  48 , such as at the entrance port  50 . The pressure differential between the high pressure fluid exiting the nozzle  48  and the lower extent  53  of the cavity  42  adjacent the nozzle  48  induces flow, such as through the entrance port  50 , referred to as an induced stream or secondary flow. 
     Referring to  FIG. 1 , the jet pump assembly  44  has an optional pressure reducer  61  located in the passage  57  formed by the inlet portion  63  of the housing  12 , upstream of the inlet  64  and the nozzle  48 . The pressure reducer  61  can instead be located further upstream of the jet pump assembly  44  such as in a vent line leading to the jet pump assembly  44 . The pressure reducer  61  reduces pressure and volume flow rate of fluid flow through the inlet portion  63  to the nozzle  48 , while increasing velocity of flow through the nozzle  48 . 
     A diffuser portion  58  of the nozzle carrier  46  is shown in  FIG. 3  supported by the housing  12 . The longitudinal passage  52  in the diffuser portion  58  is in fluid communication with a diffuser passage  59  formed by an outlet  65  of the housing  12  (best shown in  FIG. 1 ) to increase pressure and reduce velocity of the fluid. Many factors affect the performance and efficiency of the jet pump assembly  44 , including fluid molecular weight, feed temperature, position of the nozzle  48 , throat dimension, motive velocity, Reynolds number, pressure ratio, specific heat ratio, and the angle between the motive and induced stream. 
     The nozzle carrier  46  also has a carrier portion  54  extending from a first end  56  of the nozzle carrier  46  to the entrance port  50 . The diffuser portion  58  of the nozzle carrier  46  extends from the entrance port  50  to a second end  60  of the nozzle carrier  46  opposite the first end  56 .  FIGS. 4 and 7  show that there are several additional ports  50 A,  50 B,  50 C that extend through the nozzle carrier  46 , and are spaced angularly about the nozzle carrier  46  in the vicinity of the entrance port  50 . A fourth entrance port  50  is opposite port  50 C and between ports  50  and  50 B. A filter  51  shown in  FIG. 3  surrounds the nozzle carrier  46  at the port  50  to screen liquid entering the port  50  from the trap  20 . The nozzle carrier  46  has a longitudinal center axis A 1 . 
     The venturi nozzle  48  has a body portion  62  with an inlet  64 , and a nozzle portion  66  with a nozzle tip  68  forming an outlet  70 . The nozzle  48  also has a longitudinal center axis A 2 . The nozzle carrier  46  and the venturi nozzle  48  are configured so that the body portion  62  fits to the carrier portion  54  in the longitudinal passage  52 , with the nozzle portion  66  extending past the entrance port  50  so that the nozzle tip  68  is directed into the diffuser portion  58 . The fit of the body portion  62  to the carrier portion  54  is a press-fit. As shown in  FIG. 5 , the nozzle carrier  46  has spaced, radially-inwardly extending ridges  47  extending into the longitudinal passage  52  so that the body portion  62  of the venturi nozzle  48  is fit to the carrier portion  54  of the nozzle carrier  46  at the ridges  47 . 
     The nozzle  48  is inserted into the longitudinal passage  52  from the first end  56  until a first stepped shoulder  72  of the body portion  62  abuts an outer wall  55  of the nozzle carrier  46  at the first end  56 . In this position, a predetermined clearance  71  exists between the tip  68  and the inner wall of the diffuser portion  58  defining the passage  52 . 
     Alignment of the longitudinal axis A 2  of the venturi nozzle  48  with the longitudinal axis A 1  of the nozzle carrier  46  is dependent only on the nozzle carrier  46  and the venturi nozzle  48  when the venturi nozzle  48  is fit to the nozzle carrier  46  in this manner. More specifically, all other surrounding components that support the jet pump assembly  44  are configured to have larger radial clearances between the jet pump assembly  44  and the components than a clearance  67  of the tight press-fit of the body portion  62  of the nozzle  48  to the carrier portion  54  of the nozzle carrier  46 . The axes A 1 , A 2  remain substantially aligned under all operating conditions due to the controlled clearance  67 . For example, in  FIG. 3 , the carrier portion  54  is supported by the end cap  23  in a first cylindrical cavity  74  of the end cap  23 . A first clearance  76  between the end cap  23  and the carrier portion  54  is much larger than the press-fit clearance  67  of the nozzle body portion  62  to the carrier portion  54 . A clearance  73  between a first stepped portion  75  of the nozzle  48  and a cylindrical extension  77  of the end cap  23  is also larger than the clearance  67  of the nozzle  48  to the nozzle carrier  46 . Finally, a second shoulder  79  of the nozzle  48  flares outward to form a second shoulder portion  81 . A clearance  83  between the second shoulder portion  81  and the end cap  23  in the cavity  74  is larger than the press-fit clearance  67  of the nozzle  48  to the nozzle carrier  46 . A resilient ring  85  stabilizes the second shoulder portion  81  on the extension  77 . A resilient O-ring seal  87  stabilizes the first shoulder portion  75  on the extension  77 . 
     The diffuser portion  58  of the nozzle carrier  46  is press-fit to the housing  12  in a cylindrical cavity  78  of the housing  12  along only a small press-fit portion  80  of an exterior surface  84  of the diffuser portion  58 . In other words, the radial clearance  82  between the diffuser portion  58  and the housing  12  at the cavity  78  is greater in all other areas than at the press-fit portion  80 . The nozzle  48  can be a machined, deep drawn metal in order to ensure the precise press-fit clearance  67  of the nozzle  48  to the nozzle carrier  46 . The nozzle carrier  46  can be a plastic injection-molded component such as a glass-filled polyoxymethylene plastic (POM) or similar grade with a predetermined low fuel-swell performance in the presence of automotive fuel. 
     In an alternative embodiment of a jet pump assembly  144  shown in  FIG. 8 , the nozzle carrier  146  can be machined, deep drawn metal, and the nozzle  148  can be a plastic injection molded component such as a glass-filled POM or similar grade plastic with a predetermined low fuel-swell performance in the presence of automotive fuel. In still other embodiments, both the nozzle and the nozzle carrier can be a deep drawn metal, or both can be injection-molded plastic components. 
     The components of the jet pump assembly  44 , the end cap  23 , and the housing  12  are configured so that the clearances  67 ,  71 ,  73 ,  76 ,  82 ,  83  and other clearances are not less than predetermined minimum clearances under a predetermined range of operating conditions that includes a maximum fuel swell condition and a re-dry of the components from the fuel swell condition. Under this configuration, variations in the sizes of the radial clearances  67 ,  71 ,  73 ,  76 ,  79 ,  82 ,  83  will not affect the relative fit of the nozzle  48  to the nozzle carrier  46 . The assembled nozzle  48  and nozzle carrier  46  will be able to move radially as a unit relative to the end cap  23  and the housing  12 , and to rotate as a unit relative to the end cap  23  and the housing  12  about the aligned longitudinal center axes A 1 , A 2  without affecting the alignment of the longitudinal axis A 1  of the nozzle carrier  46  with the longitudinal axis A 2  of the nozzle  48 . If the entire jet pump assembly  44  rotates as a unit, the additional ports  50 A,  50 B, etc. will allow liquid to drain into the longitudinal passage  52  as one will be in communication with the lower extent  53  regardless of the position of the port  50  relative to the lower extent  53 . 
     In order for the the nozzle  48  to remain sufficiently axially aligned with the nozzle carrier  46  throughout the range of operating conditions, a constant axial compressive force should be maintained in the jet pump assembly  44 . Accordingly, the liquid trap assembly  10  provides a constant tension snap-fit between a first component (i.e., the end cap  23 ) and a second component (i.e., the housing  12 ) to create a constant axial compressive force on additional components, such as a the nozzle  48  and the nozzle carrier  46 , supported by and between the first and second components to prevent relative axial movement of the nozzle  48  and the nozzle carrier  46 . As best shown in  FIGS. 2 and 18 , the end cap  23  has a first outer surface  100  and a plurality of spaced extensions  102  and  102 A extending outward from the first outer surface  100 . The first outer surface  100  is generally cylindrical. 
     The housing  12  has a flexible rim  104  surrounding and partially defining a cavity  105 , indicated in  FIG. 1 . The cavity  105  is configured to contain a portion of the end cap  23  when the end cap  23  is partially inserted into the cavity  105 , and to contain the cavity  42  with spring  40  and check valve  36 . The flexible rim  104  is generally cylindrical and is configured to surround the first outer surface  100  when the end cap  23  is fit partially within the cavity  105 . The flexible rim  104  is shown with discrete flap portions  106  in  FIG. 2 , but could instead be continuous and unsectioned. 
     The flexible rim  104  has spaced recesses  108  that have a spacing substantially equal to the spacing of the extensions  102 ,  102 A. The rim  104  flexes to surround the end cap  23  and trap the extensions  102  in the recesses  108 . Although flexible, the rim  104  remains biased toward an unflexed state when in the flexed state shown in  FIG. 2 . The unflexed state is the position of the rim  104  when the end cap  23  is removed from the cavity  105 . In the unflexed state, the effective diameter of the rim  104  will be less than in the flexed state. In other words, the flexible rim  104  is configured with a material, such as a plastic, that has sufficient stiffness to return to a pre-stressed or unflexed state when an object or force causing the flexed state is removed. When flexed, the flexible rim  104  provides a constant radially-inward force F (i.e., a force toward the center axis A 3  of the flexible rim  104 ) as shown in  FIG. 2 . As shown in  FIG. 18 , some of the extensions  102 A have a center portion  109  that interrupts the angled surfaces and acts as an anti-rotation feature to prevent axial movement of the end cap  23  relative to the housing  12 . The end cap  23  and the housing  12  can be the same material or a different material, such as the same or different types of plastic that can swell and shrink in the presence of fuel or other medium over the range of operating conditions. 
     The extensions  102 ,  102 A and the flexible rim  104  are configured so that the extensions  102 ,  102 A will be retained in the recesses  108  and will prevent the rim  104  from returning to the unflexed state over a predetermined range of operating conditions experienced by the assembly  10  during use. As explained herein, the constant radially-inward force F of the rim  104 , illustrated at each flap portion  106  of  FIG. 2 , creates a force F 1  at the interface of each extension  102  with the rim  104  that pulls the housing  12  toward the end cap  23 , and a reaction force F 2  at the interface of each extension  102 ,  102 A with the rim  104  that pushes the end cap  23  toward the housing  12 . The forces F 1 , F 2  are maintained over the predetermined range of operating conditions due to the bias of the rim  104  toward the unflexed state. The force F 1  and reaction force F 2  are in opposite directions, and are parallel with a center axis A 3  of the end cap  23  and flexible rim  104  shown in  FIG. 1 . The center axis A 3  is in turn parallel with the aligned axes A 1 , A 2  of the nozzle  48  and nozzle carrier  46 . 
       FIGS. 12-14  show the interface of one of the extensions  102  with the flexible rim  104  in greater detail, and are representative of the interface of each of the extensions  102 ,  102 A with the rim  104 . The extension  102  shown is the lower extension of  FIG. 11  but rotated in view to show the extension  102  generally upright. The extension  102  has a base  110  with a first width W 1  at the outer surface  100  of the end cap  23 . The bottom of the extension  102  is the base  110 . Each recess  108  has a second width W 2  narrower than the first width W 1  to prevent the base  110  from fitting within the recess  108  under the predetermined range of operating conditions. In other words, the base  110  is configured to be too wide to fit within the recess  108  under the entire range of operating conditions, including swelling of the end cap  23  and housing  12  that can occur in the presence of fuel, and re-drying of the end cap  23  and housing  12  after such swelling. As shown in  FIG. 12 , the position of the rim  104  on the extension  102  is a nominal state representing operating conditions that are neither: (i) those causing a maximum swell of components; nor (ii) those causing a minimum size of the components, such as would occur without any swelling after a re-dry. 
     Each extension  102 ,  102 A has a first angled surface  112  and a second angled surface  114  that each extend from the outer surface  100  at opposite ends of the base  110  and meet at a ridge  116 . The first angled surface  112  has a first portion  118  with a first incline relative to the base  110 , and a second portion  120  with a second incline relative to the base  110 . The first portion  118  extends from the base  110  to the second portion  120 , and the second portion  120  extends from the first portion  118  to the ridge  116 . The second incline is steeper than the first incline. This is indicated in  FIG. 13  by a first angle of incline θ 1  of the first portion  118  being less than a second angle of incline θ 2  of the second portion  120 . 
     The extension  102  is configured so that an edge  122  of the flexible rim  104  at the recess  108  in which the extension  102  is retained rests along the first angled surface  112  under the entire predetermined range of operating conditions. An overall axial dimension X shown in  FIG. 3  in which the nozzle carrier  46  and nozzle  48  are constrained changes as the nozzle carrier  46 , end cap  23 , and housing  12  swell due to fuel exposure and shrink due to re-drying after exposure to fuel or other medium. Both the relative axial dimensions of these components as well as the clearances between the components change. For example,  FIG. 13  represents the relative positions of the extension  102  and the flexible rim  104  when nozzle carrier  46 , end cap  23 , and housing  12  shrink due to re-drying after exposure to fuel or other medium.  FIG. 13  represents the minimum sizes of these components under these predetermined operating conditions. In that instance, because the axial dimension X is likely to shrink, the extensions  102 ,  102 A will be axially closer to the recesses  108 , there will be less tension between the flexible rim  104  and the extensions  102 ,  102 A, and the edge  122  of the rim  104  will rest closer to the base  110  along the surface  118  than under the first predetermined operating condition of  FIG. 12 . Even under this operating condition, however, the rim  104  is prevented from returning to an unflexed state, and some force F 1  and reaction force F 2  is maintained, also acting on the nozzle carrier  46  and nozzle  48  to keep these components form relative axial movement. That is, the forces F 1 , F 2  also act at the second end  60  of the nozzle carrier  46  and the housing  12 , and at the stepped shoulder  72  and the nozzle  48 , as shown in  FIG. 3 . 
       FIG. 14  represents the relative positions of the extension  102  and the flexible rim  104  when the nozzle carrier  46 , end cap  23 , and housing  12  swell due to exposure to fuel or other medium.  FIG. 14  represents the maximum sizes of these components under all of the operating conditions. In that instance, because the axial dimension X is likely to be larger, the extensions  102 ,  102 A will be axially further from the recesses  108 , there will be greater tension between the flexible rim  104  and the extensions  102 ,  102 A, and the edge  122  of the rim  104  will rest further from the base  110  along the surface  120 . The rim  104  is prevented from returning to an unflexed state, and a force F 1  and reaction force F 2  is maintained, also acting on the nozzle carrier  46  and nozzle  48  to keep these components from relative axial movement. 
       FIGS. 15-17  show an alternate extension  202  that can be used with other like spaced extensions on the end cap  23  to interface with the flexible rim  104  in a manner that will provide a constant tension and resultant axial force on the nozzle carrier  46  and nozzle  48  under the predetermined range of operating conditions. The extension  202  has a first angled surface  212  and a second angled surface  214  both extending from a base  210  and meeting at at ridge  216 . Unlike the extension  102 , the first angled surface  212  does not have different portions with different angles of incline relative to the base  110 . 
       FIG. 15  shows the rim  104  and extension  202  in a nominal state in which the edge  122  of the rim  104  at the recess  108  interfaces with the first angled surface  212 . The rim  104  is prevented from returning to an unflexed state, and some force F 1  and reaction force F 2  is maintained at each extension  202 , also acting on the nozzle carrier  46  and nozzle  48  to keep these components from relative axial movement. 
       FIG. 16  represents the relative positions of the extension  202  and the flexible rim  104  when the nozzle carrier  46 , end cap  23 , and housing  12  shrink due to re-drying after exposure to fuel or other medium.  FIG. 16  represents the minimum sizes of these components under all of the operating conditions. In that instance, because the axial dimension X of  FIG. 3  is likely to be smaller, the extensions  202  will be axially closer to the recesses  108 , there will be less tension between the flexible rim  104  and the extensions  202 , and the edge  122  of the rim  104  will rest closer to the base  210  along the surface  212 . Even under this operating condition, the rim  104  is prevented from returning to an unflexed state, and a force F 1  and reaction force F 2  are maintained, also acting on the nozzle carrier  46  and nozzle  48  to keep these components from relative axial movement. 
       FIG. 17  represents the relative positions of the extension  202  and the flexible rim  104  when the nozzle carrier  46 , end cap  23 , and housing  12  swell due to exposure to fuel or other medium.  FIG. 17  represents the maximum sizes of these components under all of the operating conditions. In that instance, because the axial dimension X of  FIG. 3  is likely to be larger, the extensions  202  will be axially further from the recesses  108 , there will be greater tension between the flexible rim  104  and the extensions  202 , and the edge  122  of the rim  104  will rest further from the base  210  along the surface  212 . The rim  104  is prevented from returning to an unflexed state, and a force F 1  and reaction force F 2  are maintained, also acting on the nozzle carrier  46  and nozzle  48  to keep these components from relative axial movement. 
     The constant tension snap-fit ability of the extensions  102  or  202  on a first component (such as a housing  12 ) and recesses  108  on a second component (such as an end cap  23 ) could be used in other applications. In other words, an assembly other than a liquid trap assembly having the extensions and recesses with a constant tension snap-fit as described could be used to provide requisite constant axial force on other components requiring no relative axial movement. 
     The reference numbers used in the drawings and the specification along with the corresponding components are as follows:
           10  liquid trap assembly     12  housing/second component     13  upper cap     14  first port/vapor flow inlet     15  tab     16  second port/vapor flow outlet     17  tab retainer     18  interior cavity     19  filter     20  liquid trap     21  fuel vapor recovery system     22  fuel tank     23  end cap/first component     26  vapor vent valve     28  canister (C)     30  engine (E)     35  first opening of housing  12       36  check valve     38  valve body     40  spring     42  valve cavity     44  jet pump assembly     46  nozzle carrier     47  ridges     48  venturi nozzle     50  entrance port     50 A entrance port     50 B entrance port     50 C entrance port     51  filter     52  longitudinal passage of nozzle carrier     53  lower extent of cavity  42       54  carrier portion     55  wall     56  first end of nozzle carrier  46       57  passage     58  diffuser portion     59  diffuser passage     60  second end of nozzle carrier  46       61  reducer     62  body portion of nozzle  48       63  inlet portion of housing  12       64  inlet of nozzle  48       65  outlet of housing  12       66  nozzle portion     67  clearance of nozzle  48  to carrier portion  54       68  nozzle tip     70  outlet of nozzle  48       71  predetermined clearance     72  first stepped shoulder of body portion     73  clearance first stepped portion  75  and cylindrical extension  77       74  first cylindrical cavity of end cap     75  first stepped portion of nozzle  48       76  first clearance of end cap  23  to carrier portion  54       77  cylindrical extension of end cap     78  cylindrical cavity of housing  12       79  second shoulder of nozzle  48       80  press-fit portion     81  second shoulder portion     82  radial clearance of diffuser portion  58  and housing  12       83  clearance second shoulder portion  81  to end cap  23       84  exterior surface of diffuser portion  58       85  resilient ring     87  O-ring seal     90  tubing     92  fuel pump (P)     93  liquid fuel     94  fuel discharge tubing     100  first outer surface of end cap  23       102  extensions of end cap  23       102 A extensions of end cap  23       104  flexible rim of housing  12       105  cavity of housing  12       106  flap portions of rim     108  recesses in rim     109  center portion of extension  102 A     110  base of extension  102       112  first angled surface     114  second angled surface     116  ridge     118  first portion of first angled surface     120  second portion of second angled surface     122  edge of rim  104       146  nozzle carrier     148  nozzle     202  extension     210  base     212  first angled surface     214  second angled surface     216  ridge   A 1  longitudinal center axis of nozzle carrier  48     A 2  longitudinal center axis of nozzle  48     A 3  center axis of rim  104  and end cap  13     C canister   E engine   F force of rim   F 1  force of extension  102  on rim  104     F 2  reaction force of rim on extension   P pump   X axial dimension   W 1  first width of base   W 2  width of recess   θ 1  first angle of incline   θ 2  second angle of incline       

     While the best modes for carrying out the many aspects of the present teachings have been described in detail, those familiar with the art to which these teachings relate will recognize various alternative aspects for practicing the present teachings that are within the scope of the appended claims.