Passive exhaust valve assembly with overlapping slip joint and method of forming and installation

A passive exhaust valve assembly includes an exhaust conduit that has a first pipe section attached in generally axial alignment with a second pipe section. The end portion of the first pipe section includes a circumferential segment disposed within the end portion of the second pipe section to form an overlapping interface. The end portions of the first and second pipe sections each include a flange protruding radially outward from the respective first or second pipe section, whereby the flanges engage with each other to form an axle seat therebetween. A support shaft extends laterally across an interior volume of the exhaust conduit and rotatably engages the axle seat. A valve plate is coupled to the support shaft within the interior volume of the exhaust conduit for moving relative to the exhaust conduit between open and closed positions.

FIELD OF THE INVENTION

The present invention relates generally to the field of passive exhaust valves, and more particularly to spring biased valve plates assembled to pivot within an exhaust conduit and the corresponding methods of forming and installing such assemblies.

BACKGROUND OF THE INVENTION

To control back flow pressure and reduce low frequency engine noise in exhaust systems of combustion engines, it is generally understood that a passive valve may be provided in the exhaust line to alter characteristics of exhaust flow and to attenuate exhaust system noise by actuating in response to changes in exhaust pressure. Other known means for addressing these issues typically involve increasing exhaust system capacity and mass. Although passive valves can reduce exhaust system mass and weight, other potential issues with passive exhaust valve assemblies, such as valve noises, reliability, and manufacturing cost, have been deterrents to widespread adoption in combustion engine exhaust systems for vehicles.

SUMMARY OF THE PRESENT INVENTION

In accordance with one aspect of the present invention, a passive exhaust valve assembly includes an exhaust conduit having a first pipe section attached to a second pipe section with the first pipe section mated partially within the second pipe section to form an overlapping interface between end portions of the first and second pipe sections. The end portions of the first and second pipe sections each include an outward protruding flange that interrupts a circumferential segment of the overlapping interface. The outward protruding flanges align with each other to form an axle seat, whereby a support shaft extends laterally across an interior volume of the exhaust conduit and rotatably engages the axle seat. A valve plate is coupled to the support shaft within the interior volume of the exhaust conduit for operating the valve plate between open and closed positions.

Optionally, an interior surface of the first or second pipe section may include a recessed pocket that protrudes radially outward for containing a flexible bumper element, such as a metal mesh pad and/or a resilient leaf spring, arranged to contact the valve plate and dissipate impact of the valve plate moving toward the closed position. The end portion of the opposing pipe section without the recessed pocket may also include a tab that extends longitudinally to overlap with the recessed pocket and support the flexible bumper element in the recessed pocket, such as with a pair of arm portions or members that extend longitudinally to the recessed pocket to supporting edge portions of a flexible bumper element in a manner that allows movement of the flexible bumper element when resiliently flexing upon contact with valve plate.

In accordance with another aspect of the present invention, a method of assembling of a passive exhaust valve assembly includes selecting a first pipe section having an end portion with a first diameter and a second pipe section having an end portion with a second diameter, where the end portion of first pipe section is sized to mate by fitting at least partially within the end portion of the second pipe. An outward protruding flange may then be formed about the circumference at each end portion of the first and second pipe sections. A first seat portion and a second seat portion may be formed on the outward protruding flanges of the respective first and second pipe sections, such that, upon attaching the pipe sections together, alignment of the first and second seat portions form an axle seat. A circumferential section of each of the outward protruding flanges adjacent to the respective seat portion may then be bent or formed back to or near the respective original diameter of the first or second pipe section. A support shaft with a valve plate fixed to an intermediate portion of the support shaft may then be placed in one of the seat portions. The smaller diameter pipe section is then inserted within the other pipe section with the seat portions aligned to form the axle seat around the support shaft and to define an overlapping interface between the end portions of the first and second pipe sections. The overlapping interface may then be welded to attach the first pipe section to the second pipe section and form an exhaust conduit of a valve assembly.

In accordance with yet another aspect of the present invention, a method of assembling a passive exhaust valve assembly may include cutting an edge portion away from the first and second metal blanks to define a cutout area. A first seat portion may be formed at an edge of the cutout area of the first metal blank, and a second seat portion may similarly be formed at an edge of the cutout area of the second metal blank. The first metal blank may then be stamped into a tubular shape and the tubular shaped piece may be stamped with a plurality of successive dies to form a first pipe section with the first seat at an end thereof. Likewise, the second metal blank may be stamped to form a second pipe section with the second seat at an end thereof. A support shaft may then be placed in one of the first and second seat portions, where the support shaft includes a valve plate fixed to an intermediate portion of the support shaft. An end portion of the first pipe section may then be inserted within the second pipe section with the first seat portion aligned with the second seat portion to form axle seat around the support shaft. The end portion of the second pipe section overlaps the first pipe section to define an overlapping interface, which may be welded to attach the first and second pipe sections together to form an exhaust conduit.

Optionally, the overlapping interface may include an exterior surface of the first pipe section abutting an interior surface of the second pipe section, such as at the circumferential sections of the first and second pipe sections that are each bent back to the original diameter. Also, a recessed pocket may optionally be formed on an interior surface of the first or second pipe section that protrudes radially outward from an exhaust flow path that extends axially through the exhaust conduit. A flexible bumper element, such as a metal mesh pad and/or a resilient leaf spring, may optionally be placed in the recessed pocket on an interior surface of the second pipe section in a location arranged to contact the valve plate and dissipate impact of the valve plate moving toward a closed position. Further, a tab may optionally be formed at the end portion of one of the pipe sections that extends longitudinally inside the other pipe section to overlap with the recessed pocket on an interior of the other pipe section, whereby the tab supports a flexible bumper element in the recessed pocket. Such a tab may include a pair of arms or members that extend longitudinally to the recessed pocket on the interior of the other pipe section, where the pair of arms may support edge portions of a flexible bumper element disposed in the recessed pocket in a manner that allows sliding movement of the flexible bumper element at the edge portions when resiliently flexing into the recessed pocket upon contact with valve plate.

DETAILED DESCRIPTION OF EMBODIMENTS

Referring now to the drawings and the illustrative embodiments depicted therein, a passive exhaust valve assembly10,110includes an exhaust conduit12,112, such as tube or pipe, that has a support shaft or axle14,114extending laterally across an interior portion or volume16,116of the of the exhaust conduit12,112for supporting a vane or valve plate18,118or the like. The valve plate18,118is attached or coupled with the support shaft14,114to pivot within the interior volume16,116of the exhaust conduit12,112between an open position120(FIG. 19) and a closed position22,122(FIGS. 2 and 11) to regulate the flow of exhaust gases through the exhaust conduit12,112. The valve plate18,118may be biased to the closed position22,112and pivot toward the open position20when the flow of exhaust gas generates enough pressure to overcome the biasing force. To install or assemble the valve plate18,118and support shaft14,114in a pivotal manner relative to the exhaust conduit12,112, the exhaust conduit12,112may be divided into a first pipe section24,124and a second pipe section26,126that are attached to form an overlapping interface or slip joint around the support shaft14,114. Such a slip-joint arrangement may allow the valve plate18,118to be welded or otherwise attached to the support shaft14,114outside the conduit12,112prior to assembly, and may optionally allow for a flexible bumper element142, such as shown in the embodiment illustrated inFIGS. 9-23, to be attached or otherwise disposed at an interior surface of the exhaust conduit112in a location that contacts the valve plate118and dissipates impact of the valve plate118moving toward the closed position.

To form such an overlapping joint, one of the pipe sections (such as the first pipe section24,124) may be mated partially within the other pipe section (such as the second pipe section26,126) to form an overlapping interface29(FIG. 2) between end portions of the pipe sections24,26. As shown inFIG. 2, the first pipe section24has an exterior diameter24aat its end portion that is less than or substantially equal to the interior diameter26aof the second pipe section26at its end portion. It is contemplated that conversely the second pipe section may mate within the first pipe section in an additional embodiment. Also, it is conceivable that the diameter of the pipe sections may have different diameters at the central or intermediate portions that is different from the end portions, such that the end portions may be tapered or flared in other embodiments. Further, the end portions of the illustrated pipe sections24,26are cut generally perpendicular to the longitudinal extent of the pipe section, although it is conceivable that the end portions of the pipe sections may be cut at an angle to provide more or less material on the upper or lower interior surfaces, such as to form alternatively configured recesses for a bumper element or alternatively configured tabs that extend to hold the bumper element in the recess.

As illustrated, for example, inFIGS. 5-7, the end portions of the first and second pipe sections24,26each include two outward protruding flanges30. The flanges30, as shown inFIGS. 4 and 5C, interrupt and protrude outward from corresponding circumferential segments31or arcs of the overlapping interface29(FIG. 2) at the end portions of the pipe sections24,26. The illustrated outward protruding flanges30align with each other to form the axle seats32(FIG. 2) on generally opposing sides of the exhaust conduit12for rotatably engaging the shaft14. It is contemplated that each pipe section may have a single flange, such as a flange that extends along a larger segment of the circumference and interconnects between the axle seats. The support shaft14extends laterally across an interior volume of the exhaust conduit to support and position the valve plate within the interior volume16of the exhaust conduit12for pivoting the valve plate18between the open and closed positions120,22.

The end portions of the pipe sections24,26that form the overlapping interface29, such as shown inFIG. 2, have an outer surface24bof the first pipe section24abutting an inner surface26bof the second pipe section26, whereby the edges of the pipe sections24,26provide a generally consistent weld condition, which may also be referred to as a lap weld joint. The overlapping interface29between the pipe sections24,26are thereby formed by the portion34of the outer circumferential surface of the first pipe section24that is overlapped by the portion36of the inner circumferential surface of the second pipe section26. These overlapping surfaces may be in substantially continuous abutting contact, and optionally may be attached by various forms of welding, high temperature adhesives, induction shrink fitting, or fasteners or the like.

The outward protruding flanges30are shown spaced longitudinally away from the end edges of the overlapping interface29, such that the portions of the pipe sections24,26that form the overlapping interface29may define longitudinal projections that generally maintain the circular curvature of the pipe section. For example, as shown inFIGS. 5 and 5C, the end portions of the pipe sections24,26each have upper and lower longitudinal projections, shown as circumferential segments31, which are provided to form the overlapping interface29. The illustrated lower longitudinal projection extends along a greater extent of the circumference than the upper longitudinal projection, such that the axle seats32are arranged to position the support shaft14at an offset location relative to the central axis of the exhaust conduit12. It is contemplated that the upper and lower longitudinal projections in additional embodiments may instead be substantially equal in circumferential length to position the support shaft centrally across a diameter of the exhaust conduit, thereby generally intersecting the central axis.

The outward protruding flanges30, circumferential segments31, and axle seats32may be formed by a method that begins with a tubular blank. Referring toFIG. 5B, the tubular blank is first formed with a continuous flange33around the circumference of the end portion of the pipe section, as indicated with curved arrows inFIG. 5B, which flange33may include axle seats32as shown. The continuous flange33is then cut on opposite sides of the axle seats32, such as indicated with dotted lines inFIG. 5B. After these cuts are made along the flange33, the circumferential segments31are formed by bending their portions of the flange33back to or near a diameter in substantial alignment with a longitudinal extent of a main tubular shaped portion of the respective pipe section, such as indicated with curved arrows inFIG. 5C. The flanges30and axle seats32remain protruding radially outward generally orthogonal to the circumferential segments31. The respective circumferential segments31of the first and second pipe sections24,26engage to form the overlapping interface.

The outward protruding flanges30may also include an indentation38or seat portion formed on the surface of each flange30to abut together and form the axle seat38, as shown inFIG. 2. As further shown inFIG. 6, a first seat portion38ais formed on the outward protruding flanges30of the first pipe section24and a second seat portion38bis formed on the outward protruding flanges30of the second pipe section24, such that upon alignment the first and second seat portions38a,38b, the axle seat38is formed with a diameter that allows the axle seat38to engage substantially around the circumference of the support shaft14.

As shown inFIGS. 9-23, an additional embodiment of the exhaust valve assembly110provides a recessed pocket140(FIG. 11) or containment area that is disposed at an interior surface of the second pipe section126and protrudes radially outward for containing a flexible bumper element142, such as shown inFIG. 14as a metal mesh pad142aand a resilient leaf spring142b. The leaf spring142bis positioned between the interior surface of the recessed pocket140and the metal mesh pad142a, such that the mesh pad142ais arranged to contact the valve plate118, such as shown inFIG. 11, and dissipate impact of the valve plate118moving toward the closed position122. The end portion of the pipe section124without the recessed pocket may also include a tab150(FIG. 14) that extends longitudinally to overlap with the recessed pocket140and support the flexible bumper element142in the recessed pocket140. As also shown inFIGS. 11-23, such a tab150(FIG. 14) is provided with a pair of arm portions152or members that extend longitudinally to the recessed pocket140to supporting edge portions of a flexible bumper element142ain a manner that allows movement of the flexible bumper element142awhen resiliently flexing upon contact with valve plate118. With the bumper element142ain this recessed location, as shown inFIG. 11, an end portion of the valve plate118contacts the bumper element142ain or moving toward the closed position122to reduce noise generated by the valve plate118reaching the closed position122which without the bumper element may otherwise cause the valve plate or other part that pivots with the valve plate to abruptly contact a rigid surface when reaching the closed position and thereby cause an undesirable sound.

In accordance with another aspect of the present invention, a method of assembling of a passive exhaust valve assembly10,110includes selecting a first pipe section having an end portion with a first diameter and a second pipe section having an end portion with a second diameter, where the end portion of first pipe section is sized to mate by fitting at least partially within the end portion of the second pipe. An outward protruding flange33may then be formed about the circumference at each end portion of the first and second pipe sections, such as shown inFIG. 5B. A first seat portion and a second seat portion may be formed on the outward protruding flanges of the respective first and second pipe sections, such that upon mating and alignment of the first and second seat portions, an axle seat is generally formed. A circumferential section or segment31of each of the outward protruding flanges33adjacent to the respective seat portion may then be bent or formed back to or near the respective original diameter of the first or second pipe section, such as shown inFIG. 5C. A support shaft with a valve plate fixed to an intermediate portion of the support shaft may then be placed in one of the seat portions. The smaller diameter pipe section is then inserted within the other pipe section with the seat portions aligned to form the axle seat around the support shaft and to define an overlapping interface between the end portions of the first and second pipe sections. The overlapping interface may then be welded to attach the first pipe section to the second pipe section and form an exhaust conduit of a valve assembly.

In accordance with yet another aspect of the present invention, a method of assembling of a passive exhaust valve assembly includes providing first and second metal blanks, whereby an edge portion is cut from the first and second metal blanks to define a cutout area. A first seat portion may be formed at an edge of the cutout area of the first metal blank, and a second seat portion may similarly be formed at an edge of the cutout area of the second metal blank. The first metal blank may then be stamped into a tubular form and the tubular form may be stamped with a plurality of successive dies to form a first pipe section with the first seat at an end thereof. Likewise, the second metal blank may be stamped to form a second pipe section with the second seat at an end thereof. A support shaft may then be placed in one of the first and second seat portions, where the support shaft includes a valve plate fixed to an intermediate portion of the support shaft. An end portion of the first pipe section may then be inserted within the second pipe section with the first seat portion and aligned with the second seat portion to form an axle seat around the support shaft. The end portion of the second pipe section overlaps the first pipe section to define an overlapping interface, which may be welded to attach the first and second pipe sections together to an exhaust conduit.

Optionally, the overlapping interface may include an exterior surface of the first pipe section abutting an interior surface of the second pipe section, such as at the circumferential sections of the first and second pipe sections that are bent back to the original diameters. Also, a recessed pocket may optionally be formed on an interior surface of the first or second pipe section that protrudes radially outward from an exhaust flow path that extends axially through the exhaust conduit. A flexible bumper element, such as a metal mesh pad and/or a resilient leaf spring, may optionally be placed in a recessed pocket on an interior surface of the second pipe section in a location arranged to contact the valve plate and dissipate impact of the valve plate moving toward a closed position. Further, a tab may optionally be formed at the end portion of one of the pipe sections that extends longitudinally inside the other pipe section to overlap with a recessed pocket on an interior of the other pipe section, whereby the tab supports a flexible bumper element in the recessed pocket. Such a tab may include a pair of arms or members that extend longitudinally to a recessed pocket on an interior of the other pipe section, where the pair of arms may support edge portions of a flexible bumper element disposed in the recessed pocket in a manner that allows sliding movement of the flexible bumper element at the edge portions when resiliently flexing into the recessed pocket upon contact with valve plate.

The exhaust conduit of the passive exhaust valve assembly may include an inlet end and an outlet end on opposing ends of the exhaust conduit to respectively receive and dispense exhaust gases longitudinally though the exhaust conduit. The exhaust conduit may have an elongated tube or pipe shape with a curved exterior surface and a similarly curved interior surface. The interior section or volume of the exhaust conduit may thereby define a flow path along the longitudinal, central axis of the exhaust conduit, which extends generally through the internal section or volume of the exhaust conduit between the inlet and outlet ends. The valve plate may be positioned within the flow path of the internal volume and pivoted to the closed position for generally preventing exhaust gases from transferring through the tubular conduit. Although illustrated inFIGS. 1-23as a tubular shape, it is conceivable that the exhaust conduit in additional embodiments may have a different cross-sectional shape and may be curved or otherwise non-linear in the longitudinal direction.

The valve plate may be operably coupled within the interior section of the exhaust conduit and pivotal about a pivot axis between the open position, where the body portion of the valve plate is generally parallel with the exhaust flow path to provide a minimized resistance to the exhaust flow, and the closed position, where the body portion of the valve plate is at an angle that substantially reduces flow of exhaust gases through the exhaust conduit to provide a maximized resistance to the exhaust flow. The body portion of the valve plate may be rigidly coupled, such as by welding, with a support shaft or axle that defines the pivotal axis of the valve plate. The pivotal axis is generally perpendicular relative to the exhaust flow path, and, as shown, may be off-center within the exhaust conduit to define a longer portion of the valve plate and a shorter portion of the valve plate. The valve plate in the illustrated embodiments has a dimension between the upper and lower arcuate edges that is greater than the inside diameter of the exhaust conduit, such that the valve plate is oriented an angle less than ninety degrees in the closed position. However, it is contemplated that the valve plate in other embodiments may have a shape or dimension that allows it to pivot substantially perpendicular to the flow path. The valve plate may include end portions on opposing sides of a pivotal axis of the valve plate, where the short end portion of the valve plate may contact the bumper element in the close position, such as shown in the embodiment ofFIGS. 9-23. The opposing long end portion of the valve plate, such as shown with a lower arcuate edge, may be spaced from the interior surface of the exhaust conduit in the closed position, to prevent contact between the valve plate and the interior surface of the exhaust conduit and allow small amounts of exhaust gases to pass by the valve plate, which, along with the gaps on the outside edges of the valve plate, can have the tendency to reduce flutter of the valve plate.

As illustrated for example herein, the support shaft may extend through the exhaust conduit, with end portions of the support shaft pivotally engaging the axle seats or supports, which may include bushings132a(FIG. 17), on opposing sidewalls of the tubular conduit to assist with providing smooth rotational movement of the support shaft relative to the exhaust conduit. The intermediate portion of the support shaft, between the opposing ends of the internal section may be rigidly coupled with the valve plate, such that rotation or pivoting of the support shaft operates the valve plate between the open and closed positions. The valve plate may also be biased about the pivotal axis to the closed position, such as by an external spring, as shown for example inFIGS. 9-23. However, it is contemplated that a spring or other biasing device may be contained in a housing or otherwise arranged on the interior of the exhaust conduit to similarly bias the valve plate in the closed position.

In the illustrated embodiment shown inFIGS. 9-23, the axle supports132may include bushings132a(FIG. 17) that engage between the support shaft114and the outward protruding flanges130for reducing friction and noise from the rotation of the support shaft114. The bushings may include one or a combination of metal alloys, such as steel mesh, bronze, iron, ceramics, and composite materials, such as those containing carbon fibers and polymers. The bushings may include a metal wire mesh, a solid sleeve, or a combination of materials to provide a relatively low friction surface for rotation of the support shaft. The bushings may also optionally include metal wire mesh that is coated, compacted, adhered to, or otherwise integrated with a graphite material to provide additional friction resistance against the pivot rod or shaft. Specifically, a graphite powder may be compacted into the pores of the wire mesh before, after, or during the forming process of shaping the wire mesh into the bushing. In additional embodiments, it is contemplated that the axle supports may not include separate bushings or that the bushings may be integrally formed with the axle supports. It is also conceivable that the embossed indentations in other embodiments may be differently shaped and configured to be contained on more or less of the first or second pipe sections.

When the valve plate moves toward the closed position, the end portion of the valve plate may contact the bumper element142(FIG. 23) to slow and eventually cease pivotal movement of the valve plate in the closed position122. To facilitate reducing the closure speed of the valve plate, the bumper element may optionally be biased inward and toward the portion of the valve plate118that contacts the bumper element. In the illustrated example, the mesh pad142ais resiliently biased inward toward the central axis of the exhaust conduit for the end portion of the valve plate to contact the bumper element as it moves toward the closed position122(FIG. 23), and thereby gradually reduces the closure speed of the valve plate to the closed position122, further attenuating closure noises. The bumper element may be biased with an integral feature, such as a resilient mesh, or with an additional component, such as a spring142b, as shown inFIG. 23. The spring142bis illustrated as a resilient leaf spring, but may be several types of springs, such a coiled compression spring or air spring or the like.

As shown inFIGS. 22 and 23, the spring may engage between the recessed pocket140on the exhaust conduit and the bumper element142ato bias the bumper element142inward and absorb energy from the valve plate moving118toward the closed position122. Specifically, the spring is engaged in the recessed pocket of the exhaust conduit, with the ends of the leaf spring contacting the interior edge portions of the recessed pocket. The illustrated spring is oriented with its elongated extent in generally parallel alignment with the exhaust flow path and an intermediate portion of the spring contacting the mesh pad. As best illustrated inFIGS. 22 and 23, the operation of the spring is shown moving between an extended position (FIG. 22), with the valve plate in the open position or otherwise not in contact with the mesh pad, and a compressed position (FIG. 23), with the valve plate in the closed position and contacting the mesh pad.

Optionally, the bumper element142amay be floating or movably engaged within the recessed pocket140of the exhaust conduit to allow for movement of the bumper element relative to the exhaust conduit, such as in a resilient range or distance defined when the valve plate moves between the open position120and the closed position122. However, it is also contemplated that the bumper element142amay also be fixedly coupled with the exhaust conduit, such as by welding or high temperature adhesives. As shown inFIGS. 9-23, the mesh pad142ais oriented generally perpendicular to the exhaust flow path, such that it has a curvature generally corresponding to the curvature of the interior surface of the exhaust conduit. This can also be seen inFIGS. 19 and 21, whereby, in the open position120, the intermediate portion of the mesh pad142aprotrudes inward into the cylindrical shaped interior volume116of the exhaust conduit112, which is facilitated by the inward biasing force of the leaf spring.

The floating or movable engagement of the mesh pad with the exhaust conduit allows the mesh pad to have a greater range of resiliency with the spring. An example of providing such moveable engagement of the mesh pad is by at least one of the end portions of the mesh pad to be loosely or movably engaged in a channel, which can, for example, be provided between overlapping sections of the pipe sections of the exhaust conduit. The recessed pocket, such as shown inFIG. 20, has a longitudinal portion140afor the spring that is depressed away from the exhaust flow path further than a lateral portion140bof the recessed pocket140that is provided for the mesh pad142a. As shown inFIG. 19, the lateral portion of the recessed pocket may have the arm152or protrusions from the opposing pipe section extending over the edges of the mesh pad142ato provide the channel between the arm152and the lateral portion140aof the recessed pocket140for movable engagement with the mesh pad142a. Although the mesh pad is shown coupled or contacting to the spring without an attachment interface, it is contemplated that the bumper element may be fixedly attached to the spring.

For the bumper element to contact a greater surface area than the edge of the valve plate would otherwise provide, the first end portion of the valve plate may also include a stop member protruding from a body portion of the valve plate. As illustrated inFIG. 19, the stop member118ais angled from the body portion of the valve plate118and shaped to have a curved upper surface, such that the shape and orientation of the stop member118ain the closed position122(FIG. 13) may generally align with the curvature of the exhaust conduit. The curved shape of the stop member provides a larger surface area on the upper surface of the stop member to contact the bumper element in the closed position and reduce the associated closure noise.

Optionally, support shaft or axle may have an external section that is configured to stop the valve plate in the open and/or closed positions, such as illustrated inFIGS. 9-23. The external section of the support shaft angles perpendicularly from the internal section of the support shaft and extends adjacent to the exterior surface of the exhaust conduit. A distal end portion of the external section angles again perpendicularly in parallel alignment with the internal section of the support shaft to define a spring attachment point. A tension spring may thereby be secured to the spring attachment point, which may include radial protrusions from the distal end portion on opposing sides of the spring to prevent the spring from sliding laterally and disengaging from the spring attachment point on the spring arm. The external section of the support shaft is thereby shown inFIGS. 9-23to have an L-shape formed with the distal end portion. It is contemplated, however, that the external section of the pivot rod may be alternatively shaped or angled to otherwise provide a spring attachment point sufficient to attach a tension spring.

Optionally, an opposing end of the tension spring may be attached to a spring anchor that is fixed relative to the exhaust conduit, as shown for example inFIGS. 9-23, such that the tension spring may bias the external section of the support shaft in a direction that rotationally positions the valve plate toward the closed position. The spring anchor may be arranged in several ways on the exhaust conduit, such as a separate feature or integral with another component, such as an integral piece of the cover member, as shown inFIGS. 9-23. The spring anchor may be integrally formed with one of the pipe section or by being separately attached.

To stop rotation of the support shaft at an angle that corresponds with the open position of the valve plate a stop feature may optionally be provided separately or integrally with the exhaust conduit. As illustrated inFIGS. 9-23, the stop feature may include an external tab that angles rearward to an angle that abuts the external section of the support shaft with the valve plate in the open position. The external tab thereby may be configured to abut the external section of the pivot rod in a manner that reduces noise associated with the valve plate moving to the open position. It is contemplated that additional embodiments of the tab may include features for strengthening and increasing rigidity of the stop feature, and further other embodiments of the stop feature may be formed with a multitude of different shapes and configurations for abutting the pivot rod to control the positioning of the valve plate.

For purposes of this disclosure, the term “coupled” (in all of its forms, couple, coupling, coupled, etc.) generally means the joining of two components (electrical or mechanical) directly or indirectly to one another. Such joining may be stationary in nature or movable in nature; may be achieved with the two components (electrical or mechanical) and any additional intermediate members being integrally formed as a single unitary body with one another or with the two components; and may be permanent in nature or may be removable or releasable in nature, unless otherwise stated.

Changes and modifications in the specifically-described embodiments may be carried out without departing from the principles of the present invention, which is intended to be limited only by the scope of the appended claims as interpreted according to the principles of patent law including the doctrine of equivalents.