Fluid pump

A fluid pump includes an inlet plate having an inlet; an outlet plate having an outlet plate outlet passage; an outlet which discharges fluid from the fuel pump; an electric motor having a shaft which rotates about an axis; a pumping element rotationally coupled to the shaft such that rotation of the pumping element by the shaft causes fluid to be pumped from the inlet to the outlet plate outlet passage and through the outlet; and a retention clip. The retention clip includes a central portion, a first leg which extends laterally from one end of the central portion, and a second leg which extends laterally from the other end of the central portion. The inlet plate includes an inlet plate slot within which the first leg is located and the outlet plate includes an outlet plate slot within which the second leg is located.

TECHNICAL FIELD OF INVENTION

The present invention relates to a fluid pump; more particularly to a fluid pump with an inlet plate, an outlet plate, and a pumping element between the inlet plate and the outlet plate; and even more particularly to a fluid pump with retention means for retaining the inlet plate and the outlet plate to each other before the inlet plate and outlet plate are fixed within a housing of the fluid pump.

BACKGROUND OF INVENTION

Fluid pumps, and more particularly fuel pumps for pumping fuel, for example, from a fuel tank of a motor vehicle to an internal combustion engine of the motor vehicle, are known. U.S. Pat. No. 6,824,361 to Yu et al. shows a typical electric fuel pump which includes an impeller located axially between stationary inlet and outlet plates. Rotation of the impeller by an electric motor pumps fuel to an outlet of the fuel pump such that an armature of the electric motor is located in the flow path taken by the fuel in order for the fuel to reach the outlet of the fuel pump. During manufacture, the inlet plate, the impeller, and the outlet plate form a subassembly which is subsequently inserted into a housing of the fuel pump. In order to fix the inlet plate and the outlet plate within the housing, the ends of the housing are crimped, thereby applying an axial load on the inlet plate and the outlet plate which in turn prevents relative rotation between the inlet plate and the outlet plate. It is known that proper orientation of the inlet plate relative to the outlet plate is important for optimal efficiency of the fuel pump in use. However, without some way to maintain the inlet plate, impeller, and outlet plate as a subassembly prior to the ends of the housing being crimped, alignment may be compromised.

What is needed is a fluid pump which minimizes or eliminates one or more of the shortcomings as set forth above.

SUMMARY OF THE INVENTION

Briefly described, a fluid pump includes an inlet plate having an inlet; an outlet plate having an outlet plate outlet passage; an outlet which discharges fluid from the fuel pump; an electric motor having a shaft which rotates about an axis; a pumping element rotationally coupled to the shaft such that rotation of the pumping element by the shaft causes fluid to be pumped from the inlet to the outlet plate outlet passage and through the outlet, the pumping element being located axially between the inlet plate and the outlet plate; and a retention clip which includes a retention clip central portion which extends from a retention clip first end to a retention clip second end, a retention clip first leg which extends laterally from the retention clip first end and which includes a first leg inner surface, and a retention clip second leg which extends laterally from the retention clip second end and which includes a second leg inner surface such that the first leg inner surface and the second leg inner surface face toward each other; wherein the inlet plate includes an inlet plate slot within which the retention clip first leg is located and the outlet plate includes an outlet plate slot within which the retention clip second leg is located. By providing the fluid pump with the retention clip and the features of the inlet plate and the outlet plate, the inlet plate, the outlet plate, and the pumping element can be reliably be held together as a subassembly prior to the inlet plate, the outlet plate, and the pumping element being fixed within the fluid pump during manufacture.

DETAILED DESCRIPTION OF INVENTION

Reference will first be made toFIGS. 1 and 2which are an exploded isometric view and an axial cross-sectional view respectively of a fluid pump illustrated as fuel pump10for pumping liquid fuel, for example gasoline, from a fuel tank (not shown) to an internal combustion engine (not shown). While the fluid pump is illustrated as fuel pump10, it should be understood that the invention is not to be limited to a fuel pump, but could also be applied to fluid pumps for pumping fluids other than fuel. Fuel pump10generally includes a pump section12at one end, a motor section14adjacent to pump section12, and an outlet section16adjacent to motor section14at the end of fuel pump10opposite pump section12. A housing18of fuel pump10retains pump section12, motor section14and outlet section16together. Fuel enters fuel pump10at pump section12, a portion of which is rotated by motor section14as will be described in more detail later, and is pumped past motor section14to outlet section16where the fuel exits fuel pump10.

Motor section14includes an electric motor20which is disposed within housing18. Electric motor20includes a shaft22extending therefrom into pump section12. Shaft22rotates about an axis24when an electric current is applied to electric motor20. Electric motor20will be described in greater detail later.

With continued reference toFIGS. 1 and 2, pump section12includes an inlet plate26, a pumping element illustrated as impeller28, and an outlet plate30. Inlet plate26is disposed at the end of pump section12that is distal from motor section14while outlet plate30is disposed at the end of pump section12that is proximal to motor section14. Both inlet plate26and outlet plate30are fixed relative to housing18to prevent relative movement between inlet plate26and outlet plate30with respect to housing18. Outlet plate30defines a spacer ring32on the side of outlet plate30that faces toward inlet plate26. Impeller28is disposed axially between inlet plate26and outlet plate30such that impeller28is radially surrounded by spacer ring32. Impeller28is fixed to shaft22such that impeller28rotates with shaft22in a one-to-one relationship. Spacer ring32is dimensioned to be slightly thicker than the dimension of impeller28in the direction of axis24, i.e. the dimension of spacer ring32in the direction of axis24is greater than the dimension of impeller28in the direction of axis24. In this way, inlet plate26, outlet plate30, and spacer ring32are fixed within housing18, for example by crimping the axial ends of housing18. Axial forces created by the crimping process will be carried by spacer ring32, thereby preventing impeller28from being clamped tightly between inlet plate26and outlet plate30which would prevent impeller28from rotating freely. Spacer ring32is also dimensioned to have an inside diameter that is larger than the outside diameter of impeller28to allow impeller28to rotate freely within spacer ring32and axially between inlet plate26and outlet plate30. While the pumping element has been illustrated as impeller28, it should now be understood that other pumping elements may alternatively be used, by way of non-limiting example only, a gerotor, gears, or roller vanes. Furthermore, while spacer ring32is illustrated as being made as a single piece with outlet plate30, it should be understood that spacer ring32may alternatively be made as a separate piece that is captured axially between outlet plate30and inlet plate26.

Inlet plate26is generally cylindrical in shape, and includes an inlet34that extends through inlet plate26in the same direction as axis24. Inlet34is a passage which introduces fuel into fuel pump10. Inlet plate26also includes an inlet plate flow channel36formed in the face of inlet plate26that faces toward impeller28. Inlet plate flow channel36is in fluid communication with inlet34.

Outlet plate30is generally cylindrical in shape and includes an outlet plate outlet passage40that extends through outlet plate30in the same direction as axis24where it should be noted that outlet plate outlet passage40is an outlet for pump section12. Outlet plate outlet passage40is in fluid communication with outlet section16as will be describe in more detail later. Outlet plate30also includes an outlet plate flow channel42formed in the face of outlet plate30that faces toward impeller28. Outlet plate flow channel42is in fluid communication with outlet plate outlet passage40. Outlet plate30also includes an outlet plate aperture, hereinafter referred to as lower bearing44, extending through outlet plate30. Shaft22extends through lower bearing44in a close fitting relationship such that shaft22is able to rotate freely within lower bearing44and such that radial movement of shaft22within lower bearing44is limited to the manufacturing tolerances of shaft22and lower bearing44. In this way, lower bearing44radially supports a lower end46of shaft22that is proximal to pump section12.

Impeller28includes a plurality of impeller blades48arranged in a polar array radially surrounding and centered about axis24such that impeller blades48are aligned with inlet plate flow channel36and outlet plate flow channel42. Impeller blades48are each separated from each other by an impeller blade chamber49that passes through impeller28in the general direction of axis24. Impeller28may be made, for example only, by a plastic injection molding process in which the preceding features of impeller28are integrally molded as a single piece of plastic.

Outlet section16includes an end cap50having an outlet52for discharging fuel from fuel pump10. Outlet52may be connected to, for example only, a conduit (not shown) for supplying fuel to an internal combustion engine (not shown). Outlet52is in fluid communication with outlet plate outlet passage40of outlet plate30for receiving fuel that has been pumped by pump section12.

With continued reference toFIGS. 1 and 2and with additional reference toFIGS. 3-6, electric motor20includes a rotor or armature54with a plurality of circumferentially spaced motor windings56, and a commutator portion58where shaft22extends in each direction from armature54such that armature54rotates about axis24. Electric motor20also includes a stator59with a motor frame60, a pair of permanent magnets62, and a flux carrier64. Each magnet62is in the shape of a segment of a hollow cylinder. Stator59circumferentially surrounds armature54such that a fluid passage65is defined radially between armature54and stator59and such that fuel flows axially through fluid passage65from inlet34to outlet52. Motor frame60includes a top section66that is proximal to outlet section16, a plurality of circumferentially spaced legs68extending axially from top section66toward pump section12, and a base section70axially spaced apart from top section66by legs68. Top section66, legs68, and base section70are preferably integrally formed from a single piece of plastic, for example only, by a plastic injection molding process.

Top section66of motor frame60includes a first electrical terminal72and a second electrical terminal74extending therefrom and protruding through end cap50. First electrical terminal72and second electrical terminal74are arranged to be connected to a power source (not shown) such that first electrical terminal72and second electrical terminal74are opposite in polarity. First electrical terminal72and second electrical terminal74may be disposed within pre-formed openings in top section66or first electrical terminal72and second electrical terminal74may be insert molded with top section66when motor frame60is formed by a plastic injection molding process. First electrical terminal72is in electrical communication with a first carbon brush76while second electrical terminal74is in electrical communication with a second carbon brush78. First carbon brush76is disposed within a first brush holder80that is defined by top section66and is urged into contact with commutator portion58of armature54by a first brush spring82that is grounded to end cap50. Second carbon brush78is disposed within a second brush holder84defined by top section66and is urged into contact with commutator portion58of armature54by a second brush spring86that is grounded to end cap50. First carbon brush76and second carbon brush78deliver electrical power to motor windings56via commutator portion58, thereby rotating armature54and shaft22about axis24in use.

Top section66of motor frame60defines an upper bearing88therein which radially supports an upper end90of shaft22that is proximal to outlet section16. Shaft22is able to rotate freely within upper bearing88such that radial movement of shaft22within upper bearing88is limited to the manufacturing tolerances of shaft22and upper bearing88.

Legs68are preferably equally circumferentially spaced around top section66and base section70and define motor frame openings92between legs68. Motor frame openings92extend axially from top section66to base section70. One magnet62is disposed within each motor frame opening92and magnets62may be inserted within respective motor frame openings92after motor frame60has been formed. Alternatively, magnets62may be insert molded with motor frame60when motor frame60is formed by a plastic injection molding process. In this way, magnets62and legs68radially surround armature54. While two legs68and two magnets62have been illustrated, it should be understood that other quantities of legs68and magnets62may be used.

Base section70may be annular in shape and connects legs68to each other. Base section70includes a base section recess94extending axially thereinto from the end of base section70that faces away from top section66. Base section recess94is coaxial with upper bearing88and receives outlet plate30closely therein such that radial movement of outlet plate30within base section recess94is substantially prevented. Since base section recess94is coaxial with upper bearing88, a coaxial relationship is maintained between lower bearing44and upper bearing88by base section70. Base section70also defines an annular shoulder96that faces toward top section66. Annular shoulder96may be substantially perpendicular to axis24.

Flux carrier64is made of a ferromagnetic material and may take the form of a cylindrical tube. Flux carrier64closely radially surrounds legs68of motor frame60and magnets62. Flux carrier64may be made, for example only, from a sheet of ferromagnetic material formed to shape by a rolling process. The end of flux carrier64that is proximal to base section70of motor frame60axially abuts annular should96of base section70while the end of flux carrier64that is proximal to top section66of motor frame60axially abuts a portion of end cap50that radially surrounds top section66of motor frame60. In this way, flux carrier64is captured axially between end cap50and annular shoulder96of base section70.

Since motor frame60may be made as a single piece, for example only, by a plastic injection molding process, upper bearing88and base section recess94can be made by a single piece of tooling, thereby allowing a high degree of control over the relative positions of upper bearing88and base section recess94. Consequently, lower bearing44can more easily be maintained in a coaxial relationship with upper bearing88. Similarly, since first brush holder80and second brush holder84may be defined by top section66, for example only, by an injection molding process, first brush holder80, second brush holder84, and upper bearing88may be formed by a single piece of tooling, thereby allowing a high degree of control over the relative positions of first brush holder80, second brush holder84, and upper bearing88. Consequently, first brush holder80and second brush holder84can be easily maintained parallel to axis24which may be important for first carbon brush76and second carbon brush78to adequately interface with commutator portion58of armature54.

In operation, inlet34is exposed to a volume of fuel (not shown) which is to be pumped to, for example only, an internal combustion engine (not shown). An electric current is supplied to motor windings56in order to rotate shaft22and impeller28. As impeller28rotates, fuel is drawn through inlet34into inlet plate flow channel36. Impeller blade chambers49allow fuel from inlet plate flow channel36to flow to outlet plate flow channel42. Impeller28subsequently discharges the fuel through outlet plate outlet passage40and consequently through outlet52.

For proper operation and maximum efficiency, it is important to ensure proper orientation of inlet plate26relative to outlet plate30about axis24. Unless somehow constrained, orientation of inlet plate26relative to outlet plate30about axis24may vary until inlet plate26and outlet plate30are fixed relative to housing18to prevent relative movement between inlet plate26and outlet plate30with respect to housing18, for example, by crimping the axial ends of housing18as mentioned previously. In the paragraphs that follow and with particular reference toFIGS. 6-12, features of inlet plate26and outlet plate30will be described which maintain inlet plate26, outlet plate30, and impeller28as a subassembly prior to being fixed within housing18during manufacture of fuel pump10and which ensure proper orientation of inlet plate26relative to outlet plate30about axis24.

In order to retain inlet plate26, outlet plate30, and impeller28as a subassembly as shown inFIGS. 6 and 7and in order to maintain proper orientation of inlet plate26relative to outlet plate30, retention clips98are provided which engage complementary features of inlet plate26and outlet plate30. While two retention clips98have been illustrated, it should be understood that a lesser or greater number of retention clips98may be utilized. Since each retention clip98may be substantially identical, only one retention clip98will be described in detail herein with the understanding that the description of retention clip98herein is equally applicable to each retention clip98.

Retention clip98may be made of metal for, for example stainless steel or coated steel, and includes retention clip central portion100which extends from a retention clip first end102to a retention clip second end104in a first direction. Retention clip central portion100includes a central portion inner surface100awhich faces toward axis24; a central portion outer surface100bwhich is opposed to, and parallel with, central portion inner surface100aand faces away from axis24; a central portion first edge100c; and a central portion second edge100dsuch that central portion inner surface100aand central portion outer surface100beach extend from central portion first edge100cto central portion second edge100dfor a central portion width100ein a second direction that is perpendicular to the first direction. As can be seen most clearly inFIG. 7, retention clip central portion100is located radially outward from impeller28.

Retention clip98also includes a retention clip first leg106which extends laterally from retention clip first end102toward axis24. Retention clip first leg106includes a first leg inner surface106awhich intersects with central portion inner surface100a; a first leg outer surface106bwhich is opposed to, and parallel with, first leg inner surface106asuch that first leg outer surface106bintersects with central portion outer surface100b; a first leg first edge106c; and a first leg second edge106dsuch that first leg inner surface106aand first leg outer surface106beach extend from first leg first edge106cto first leg second edge106din the second direction.

Retention clip98also includes a retention clip second leg108which extends laterally from retention clip second end104toward axis24. Retention clip second leg108includes a second leg inner surface108awhich intersects with central portion inner surface100a; a second leg outer surface108bwhich is opposed to, and parallel with, second leg inner surface108asuch that second leg outer surface108bintersects with central portion outer surface100b; a second leg first edge108c; and a second leg second edge108dsuch that second leg inner surface108aand second leg outer surface108beach extend from second leg first edge108cto second leg second edge108din the second direction. As shown in the figures, first leg inner surface106aand second leg inner surface108aface toward each other, and in this way, retention clip98has a generally C-shaped cross-section when sectioned by a plane which passes through retention clip central portion100, retention clip first leg106, and retention clip second leg108.

Inlet plate26includes an inlet plate outer peripheral surface26awhich surrounds axis24and which faces away from axis24toward a housing inner surface18aof housing18. An inlet plate slot110extends into inlet plate26from inlet plate outer peripheral surface26aand receives retention clip first leg106therein and an inlet plate groove112extends into inlet plate26from the inlet plate outer peripheral surface26aand receives a portion of retention clip central portion100therein.

Inlet plate slot110includes an inlet plate slot first surface110awhich faces toward, and contacts, first leg inner surface106awhen retention clip first leg106is inserted within inlet plate slot110; an inlet plate slot second surface110bwhich faces toward first leg outer surface106bwhen retention clip first leg106is inserted within inlet plate slot110; an inlet plate slot first edge110cwhich faces toward first leg first edge106cwhen retention clip first leg106is inserted within inlet plate slot110; and an inlet plate slot second edge110dwhich faces toward first leg second edge106dwhen retention clip first leg106is inserted within inlet plate slot110such that inlet plate slot first surface110aand inlet plate slot second surface110beach extend from inlet plate slot first edge110cto inlet plate slot second edge110d. Inlet plate slot110is terminated by an inlet plate slot end wall110ewhich intersects with each of inlet plate slot first surface110a, inlet plate slot second surface110b, inlet plate slot first edge110c, and inlet plate slot second edge110d. As can be seen in the figures, retention clip first leg106is peripherally surrounded by inlet plate slot110when retention clip first leg106is inserted within inlet plate slot110.

Inlet plate groove112extends into inlet plate26from the inlet plate outer peripheral surface26asuch that inlet plate groove112intersects with inlet plate slot110and extends parallel to axis24to the face of inlet plate26that faces toward impeller28and outlet plate30/spacer ring32. Inlet plate groove112includes an inlet plate groove first surface112awhich faces away from axis24which faces toward central portion inner surface100aof retention clip central portion100when retention clip central portion100is inserted within inlet plate groove112; an inlet plate groove first edge112cwhich faces toward central portion first edge100cof retention clip central portion100when retention clip central portion100is inserted within inlet plate groove112; and an inlet plate groove second edge112dwhich faces toward central portion second edge100dof retention clip central portion100when retention clip central portion100is inserted within inlet plate groove112such that inlet plate groove first surface112aextends from inlet plate groove first edge112cto inlet plate groove second edge112dfor an inlet plate groove width112ein the second direction.

Outlet plate30includes an outlet plate outer peripheral surface30awhich surrounds axis24and which faces away from axis24toward housing inner surface18aof housing18. An outlet plate slot114extends into outlet plate30from outlet plate outer peripheral surface30aand receives retention clip second leg108therein and an outlet plate groove116extends into inlet plate26from the outlet plate outer peripheral surface30aand receives a portion of retention clip central portion100therein.

Outlet plate slot114includes an outlet plate slot first surface114awhich faces toward, and contacts, second leg inner surface108awhen retention clip second leg108is inserted within outlet plate slot114; an outlet plate slot second surface114bwhich faces toward second leg outer surface108bwhen retention clip second leg108is inserted within outlet plate slot114; an outlet plate slot first edge114cwhich faces toward second leg first edge108cwhen retention clip second leg108is inserted within outlet plate slot114; and an outlet plate slot second edge114dwhich faces toward second leg second edge108dwhen retention clip second leg108is inserted within outlet plate slot114such that outlet plate slot first surface114aand outlet plate slot second surface114beach extend from outlet plate slot first edge114cto outlet plate slot second edge114d. Outlet plate slot114is terminated by an outlet plate slot end wall114ewhich intersects with each of outlet plate slot first surface114a, outlet plate slot second surface114b, outlet plate slot first edge114c, and outlet plate slot second edge114d. As can be seen in the figures, retention clip second leg108is peripherally surrounded by outlet plate slot114when retention clip second leg108is inserted within outlet plate slot114.

Outlet plate groove116extends into outlet plate30from the outlet plate outer peripheral surface30asuch that outlet plate groove116intersects with outlet plate slot114and extends parallel to axis24to the face of spacer ring32which faces toward inlet plate26. Outlet plate groove116includes an outlet plate groove first surface116awhich faces away from axis24and which faces toward central portion inner surface100aof retention clip central portion100when retention clip central portion100is inserted within outlet plate groove116; an outlet plate groove first edge116cwhich faces toward central portion first edge100cwhen retention clip central portion100of retention clip central portion100is inserted within outlet plate groove116; and an outlet plate groove second edge116dwhich faces toward central portion second edge100dwhen retention clip central portion100of retention clip central portion100is inserted within outlet plate groove116such that outlet plate groove first surface116aextends from outlet plate groove first edge116cto outlet plate groove second edge116dfor an outlet plate groove width116ein the second direction.

Retention clip central portion100, inlet plate groove112, and outlet plate groove116are made such that central portion width100e, inlet plate groove width112e, and outlet plate groove width116eare sized in order to limit the magnitude to which inlet plate26and outlet plate30are able to rotate relative to each other about axis24prior to being fixed within housing18. As should now be clear, the difference between central portion width100eand inlet plate groove width112eand the difference between central portion width100eand outlet plate groove width116edetermine the magnitude to which inlet plate26and outlet plate30are able to rotate relative to each other about axis24prior to inlet plate26and outlet plate30being fixed within housing18. Preferably, these differences are sized to allow less than 1° rotation about axis24between inlet plate26and outlet plate30, however, a practitioner of ordinary skill in the art will be able to determine the allowable magnitude of rotation that provides the desired efficiency of fuel pump10and be able to size central portion width100e, inlet plate groove width112e, and outlet plate groove width116eaccordingly to achieve this allowable magnitude of rotation.

While retention clip central portion100is provided to limit rotation of inlet plate26and outlet plate30about axis24prior to inlet plate26and outlet plate30being fixed within housing18, retention clip first leg106and retention clip second leg108are provided to prevent separation between inlet plate26and outlet plate30in the direction of axis24prior to inlet plate26and outlet plate30being fixed within housing18. This is accomplished by sizing a distance118(best seen inFIG. 9between first leg inner surface106aand second leg inner surface108ato be complementary to a distance120(best seen inFIG. 12) between inlet plate slot first surface110aand outlet plate slot first surface114awhen inlet plate26is assembled to outlet plate30. It should be noted that prior to inserting retention clip first leg106and retention clip second leg108into inlet plate slot110and outlet plate slot114respectively, distance118may be less than distance120. In this way, inserting retention clip first leg106and retention clip second leg108into inlet plate slot110and outlet plate slot114respectively results in resilient deflection of retention clip first leg106relative to retention clip second leg108such that first leg inner surface106acontacts inlet plate slot first surface110aand second leg inner surface108acontacts outlet plate slot inner surface114a, and consequently, inlet plate26and outlet plate30are held in compression with each other between retention clip first leg106and retention clip second leg108. Alternatively, distance118and distance120may be substantially the same prior to inserting retention clip first leg106and retention clip second leg108into inlet plate slot110and outlet plate slot114respectively, and consequently, first leg inner surface106acontacts inlet plate slot first surface110aand second leg inner surface108acontacts outlet plate slot inner surface114a, however, compression is not provided to inlet plate26and outlet plate30.

In order to ensure retention of retention clip98, additional features be provided which engage inlet plate slot110and outlet plate slot114as will be described with respect toFIGS. 13 and 14. In a first example as shown inFIG. 13, a retention clip198is shown where elements of retention clip98that are similar are provided with reference numbers increased in number by one-hundred. Unlike retention clip98which has first leg outer surface106band second leg outer surface108bwhich are planar, retention clip198includes first leg outer surface206band second leg outer surface208bwhich each include one or more barbs206eand one or more barbs208erespectively. Barbs206etaper from a smaller cross-sectional area proximal inlet plate slot end wall110e(shown in phantom lines inFIG. 13) to a larger cross-sectional area distal from inlet plate slot end wall110e, and similarly, barbs208etaper from a smaller cross-sectional area proximal outlet plate slot end wall114eto a larger cross-sectional area distal from outlet plate slot end wall114e. In this way, barbs206eand barbs208eengage inlet plate slot second surface110b(shown in phantom lines inFIG. 13) and outlet plate slot second surface114b(shown in phantom lines inFIG. 13) respectively, thereby allowing for easy insertion of retention clip198while inhibiting removal of retention clip198.

In a second example shown inFIG. 14, a retention clip298is shown where elements of retention clip98that are similar are provided with reference numbers increased in number by two-hundred. Unlike retention clip98which has first leg first edge106c, first leg second edge106d, second leg first edge108c, and second leg second edge108dwhich are planar, retention clip298includes first leg first edge306cand first leg second edge306dwhich each include one or more barbs306eand also includes second leg first edge308cand second leg second edge308dwhich each include one or more barbs308e. Barbs306etaper from a smaller cross-sectional area proximal inlet plate slot end wall110eto a larger cross-sectional area distal from inlet plate slot end wall110e, and similarly, barbs308etaper from a smaller cross-sectional area proximal outlet plate slot end wall114eto a larger cross-sectional area distal from outlet plate slot end wall114e. In this way, barbs206eengage inlet plate slot first edge110cand inlet plate slot second edge110dand barbs208eengage outlet plate slot first edge114cand outlet plate slot second edge114d, thereby allowing for easy insertion of retention clip298while inhibiting removal of retention clip298. In order to provide further retention, a first leg retention slot306fmay be provided in retention clip first leg306such that first leg retention slot306fextends from first leg inner surface306ato first leg outer surface306b. In this way, first leg first edge306cand first leg second edge306dare resiliently deflected inward when retention clip first leg306is inserted into inlet plate slot110. Similarly, a second leg retention slot308fmay be provided in retention clip second leg308such that second leg retention slot308fextends from second leg inner surface308ato second leg outer surface308b. In this way, second leg first edge308cand second leg second edge308dare resiliently deflected inward when retention clip second leg308is inserted into outlet plate slot114. While retention clip298has been illustrated herein as including first leg retention slot306fand second leg retention slot308f, it should be understood that these features may alternatively be omitted.

Retention clips98,198, and298as described herein together with the complementary features of inlet plate26and outlet plate30provide for reliable positioning and retention of inlet plate26relative to outlet plate30prior to fixing of inlet plate26and outlet plate30within housing18.

While this invention has been described in terms of preferred embodiments thereof, it is not intended to be so limited, but rather only to the extent set forth in the claims that follow.