Seal for an Exhaust System

A portion of a typical automotive exhaust system is shown schematically in FIG. 1 of the drawings. This system usually comprises a header which in some instances is made of steel to provide low back pressure, rapid acceleration and high fuel economy. The system has a stepped down tail pipe section which may include a catalytic converter and a muffler. The juncture of the header manifold and tail pipe section usually includes a flange connection which is secured by bolts which compress a gasket at the interface of the flanges.

A typical gasket materials is cork impregnated with asbestos. The confronting flange surfaces are rather narrow in a radial direction. By reason of this and also due to heat expansion and contraction in the exhaust systems, torsional shear forces are exerted on the gasket which produce cracking and associated exhaust leakage. Exhaust leakage in a passenger vehicle can be lethal. Furthermore, deterioration and failure of the gasket usually produces rattling and objectionable noise from the exhaust system. Most States now monitor exhaust systems and during periodic required inspections, will require replacement for leaky or noisy exhaust systems.

The present invention provides a seal particularly adapted for exhaust systems, which is characterized by novel features of construction and arrangement which overcomes the disadvantages of prior seals used for this purpose. The seal of the present invention provides a long lasting and secure means of sealing the junction between the header and exhaust pipe mating flange members.

To this end, the seal consists of an inner annular sealing ring-like member made of a deformable material, for example a non-asbestos materials such as polyamids and a metallic outer spacer or retainer ring preferably made of steel, disposed between the flanges of the header and exhaust pipe and which circumscribes the annular ring member. In the relaxed state, the inner annular ring member is preferably of a larger axial cross-section than the axial cross-section of the metallic outer retainer ring, such as, perhaps two or three times thicker. In the relaxed state, the largest outer diameter of the inner annular member is slightly smaller than the bore diameter of the outer retainer ring. Further, the outer peripheral surface of the annular member is preferably contoured and includes at least a portion of a greater diameter than the header opening at the junction of the exhaust manifold and tail pipe section. In this manner when the annular member and retainer ring are placed between the flanges and the exhaust manifold and tail pipe section flanges are pressed together by conventional bolts, the annular member is deformed in a radial direction to press tightly against the inner bore of the retainer ring and the contoured outer peripheral surface of the annular member overlies the axial portion of the junction between the manifold section and tail pipe adjacent the flanges. This provides a large surface contact with the annular member and the critical sealing area at the junction of the exhaust manifold and tail pipe section.

The installed seal of the present invention provides a large internal seal area that resists heat and pressure which develop in the exhaust system. Further, the internal back pressure acts on the seal in a manner to expand the sealing surfaces and aids in producing the large seal area, which inhibits escape of noxious exhaust gases and the like.

Further, the inner annular member is preferably made of a material which is capable of withstanding the temperature of the exhaust gases and is resistant to chemical deterioration to thereby preserve the integrity of the seal for a long period of time. As noted above, non-asbestos fibers such as polyamid fibers, manufactured by DuPont under the registered trademark Kevlar, are suitable materials for the inner ring. Similarly, the outer ring is formed of metal, preferably stainless steel in order to resist heat and corrosion.

These and other objects of the present invention and the various features and details of the operation and construction thereof are hereinafter more fully set forth with reference to the accompanying drawings, wherein;

FIG. 1 is a schematic illustration showing some of the parts of a typical automotive exhaust system including a header section and a tail pipe section;

FIG. 2 is an enlarged sectional view taken on lines 2--2 of FIG. 1;

FIG. 3 is an exploded perspective view of the elements comprising a seal made in accordance with the present invention;

FIG. 4 is an exploded side elevational view partly in section showing the parts of the seal and manifold and tail pipe section prior to assembly of the seal;

FIG. 5 is a side elevational view partly in section showing the seal in an assembled condition, the dot and dash portion shown in FIG. 1;

FIG. 6 is a typical prior art seal used for connecting the header and tail pipe sections; and

FIG. 7 is an enlarged fragmentary view of the assembled seal shown in the dot and dash circle of FIG. 5.

Referring now to the drawings and particularly to FIG. 1 thereof, there is shown schematically a typical automotive exhaust system generally designated by the numeral 10 which includes a header section 12 and a tail pipe section 14. The tail pipe section 14 may include a catalytic converter and a muffler downstream of the header. The header section 12 and tail pipe section 14 have circumferentially extending radially outwardly directed flanges 20 and 22 including a series of circumferentially spaced aligned bolt holes 20a and 22a for bolt 25 and nut 27 fasteners.

This junction of the two flanges 20 and 22 is sealed by a flat ring like gasket 28 prior to the present invention in the manner illustrated in FIG. 6. This gasket type seal presents disadvantages and draw backs discussed above. These disadvantages may be summarized by the tact that these seals do not withstand the torsion loads and other conditions that tend to cause leakage paths so that the gasket 28 will often fail prematurely creating noise and potential health problems.

The seal of the present invention is characterized by novel features of construction and arrangement facilitating a tight long term seal between the flanges of the sections of the exhaust system described above. The seal of the present invention provides a large effective surface area sealing at the juncture of the flanges.

More specifically, the seal of the present invention comprises two annular sealing members, an inner annular sealing ring like member 40 made of a deformable material, such as non-asbestos fibers admixed with steel wire, and an outer spacer or retainer ring 42 preferably made of steel circumscribing the annular ring member 40 and radially spaced therefrom to define a circumferentially extending gap G. The bore 44 of the outer retainer ring 42 is preferably circular and of a diameter D1 slightly greater than the maximum diameter D of the inner annular ring member 40 in the relaxed state. Further, the inner annular ring member 40 is preferably of a larger axial width W greater than the thickness T of the outer retainer ring 42.

In the present instance, the annular ring member 40 has a generally cylindrical bore 46 and has a contoured outer peripheral surface 48, consisting in the present instance of two circumferentially extending tapered frusto conical outer faces 48a and 48b connected by a short generally cylindrical center section 48c. In this manner, the inner edge 60 defined by the flange 20 of the manifold section 12 and the inner edge 62 of the flange 22 defined by the tail pipe section 14 engage at about the mid point of the opposing tapered frusto conical faces 48a and 48b of the inner annular ring member 40 when the seal is positioned between the flange members 20 and 22 as shown in FIG. 4.

Thereafter, when the flanges 20 and 22 are drawn together by tightening the bolts 25 to a position where they are spaced apart by the thickness T of the metallic retainer ring 42, the inner edges 60 and 62 press against the opposing tapered faces 48a and 48b to deform the annular ring member 40 so that the seal presses tightly at the junction of the parts in the manner shown in FIG. 7. Note that the material of the annular ring member 40 overlies and presses tightly against the circumferentially extending surfaces adjacent the edges 60 and 62.

The following is an example of a seal in accordance with the present invention for a typical automotive exhaust system wherein the header 12 has an inside diameter D2 of 2.875 inches, as does the portion of tail pipe 14 at flange 22.

Of course, different exhaust systems have different sized headers and tail pipes or exhaust pipes, and the seal of the present invention will need to be sized to accommodate those dimensions. Most automobile exhaust systems can be sealed by the present invention using one of about three general sizes.

The installed seal of the present invention provides a large internal seal area that resists the effects of heat and pressure which develop in the exhaust system. Further, the internal back pressure acts on the seal in a manner to expand the sealing surfaces and aids in producing the large seal area, which practically eliminates the escape of noxious exhaust gases and the like.

Even though a particular embodiment of the invention has been illustrated and described herein, it is not intended to limit the invention and changes and modifications maybe be made therein within the scope of the following claims: