WO1991002143A1 - Insulated exhaust pipe and method and means for producing and connecting same - Google Patents

Insulated exhaust pipe and method and means for producing and connecting same Download PDF

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Publication number
WO1991002143A1
WO1991002143A1 PCT/US1990/004253 US9004253W WO9102143A1 WO 1991002143 A1 WO1991002143 A1 WO 1991002143A1 US 9004253 W US9004253 W US 9004253W WO 9102143 A1 WO9102143 A1 WO 9102143A1
Authority
WO
WIPO (PCT)
Prior art keywords
tube
pipe
insulation
insulated
conduit
Prior art date
Application number
PCT/US1990/004253
Other languages
French (fr)
Inventor
David William Bainbridge
William Harrison Olbert
Original Assignee
Manville Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to US386,841 priority Critical
Priority to US07/386,754 priority patent/US5004018A/en
Priority to US07/386,841 priority patent/US4998597A/en
Priority to US386,754 priority
Application filed by Manville Corporation filed Critical Manville Corporation
Publication of WO1991002143A1 publication Critical patent/WO1991002143A1/en

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Classifications

    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16LPIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
    • F16L59/00Thermal insulation in general
    • F16L59/14Arrangements for the insulation of pipes or pipe systems
    • F16L59/16Arrangements specially adapted to local requirements at flanges, junctions, valves or the like
    • F16L59/18Arrangements specially adapted to local requirements at flanges, junctions, valves or the like adapted for joints
    • F16L59/184Flanged joints
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N13/00Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
    • F01N13/14Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having thermal insulation
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N13/00Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
    • F01N13/14Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having thermal insulation
    • F01N13/141Double-walled exhaust pipes or housings
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N13/00Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
    • F01N13/18Construction facilitating manufacture, assembly, or disassembly
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N13/00Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
    • F01N13/18Construction facilitating manufacture, assembly, or disassembly
    • F01N13/1805Fixing exhaust manifolds, exhaust pipes or pipe sections to each other, to engine or to vehicle body
    • F01N13/1811Fixing exhaust manifolds, exhaust pipes or pipe sections to each other, to engine or to vehicle body with means permitting relative movement, e.g. compensation of thermal expansion or vibration
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N13/00Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
    • F01N13/18Construction facilitating manufacture, assembly, or disassembly
    • F01N13/1805Fixing exhaust manifolds, exhaust pipes or pipe sections to each other, to engine or to vehicle body
    • F01N13/1811Fixing exhaust manifolds, exhaust pipes or pipe sections to each other, to engine or to vehicle body with means permitting relative movement, e.g. compensation of thermal expansion or vibration
    • F01N13/1816Fixing exhaust manifolds, exhaust pipes or pipe sections to each other, to engine or to vehicle body with means permitting relative movement, e.g. compensation of thermal expansion or vibration the pipe sections being joined together by flexible tubular elements only, e.g. using bellows or strip-wound pipes
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16LPIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
    • F16L59/00Thermal insulation in general
    • F16L59/14Arrangements for the insulation of pipes or pipe systems
    • F16L59/153Arrangements for the insulation of pipes or pipe systems for flexible pipes
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16LPIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
    • F16L59/00Thermal insulation in general
    • F16L59/14Arrangements for the insulation of pipes or pipe systems
    • F16L59/16Arrangements specially adapted to local requirements at flanges, junctions, valves or the like
    • F16L59/21Arrangements specially adapted to local requirements at flanges, junctions, valves or the like adapted for expansion-compensation devices
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2310/00Selection of sound absorbing or insulating material
    • F01N2310/02Mineral wool, e.g. glass wool, rock wool, asbestos or the like
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2450/00Methods or apparatus for fitting, inserting or repairing different elements
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2450/00Methods or apparatus for fitting, inserting or repairing different elements
    • F01N2450/22Methods or apparatus for fitting, inserting or repairing different elements by welding or brazing
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2450/00Methods or apparatus for fitting, inserting or repairing different elements
    • F01N2450/24Methods or apparatus for fitting, inserting or repairing different elements by bolts, screws, rivets or the like
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2450/00Methods or apparatus for fitting, inserting or repairing different elements
    • F01N2450/28Methods or apparatus for fitting, inserting or repairing different elements by using adhesive material, e.g. cement
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01NGAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2470/00Structure or shape of gas passages, pipes or tubes
    • F01N2470/24Concentric tubes or tubes being concentric to housing, e.g. telescopically assembled

Abstract

An insulated exhaust pipe (10) comprising inner and outer spaced corrugated metallic tubes (12, 14) separated by a layer of low density refractory fiber insulation (16) and strips of higher density refractory fibers insulation (18). The pipe (10) is made by adhering the insulation (18) to the inner tube (12) and inserting the insulated inner tube (12) into the outer tube (14) while rotating it so that the corrugations (22) of the outer tube (14) do not damage the insulation (18). Attachment means (134) for connecting a corrugated insulated pipe (154) to an element in the exhaust system means include a conduit (130) having a transverse lug (138) which allows the conduit (130) to be threaded into the pipe (154). The end of the pipe (154) is received in an end cap (142) slidably mounted on the conduit (130). A stop (140) on the conduit (130) limits relative movement of the pipe (154) and conduit (130), permitting the connection between the pipe (154) and conduit to be tightened.

Description

INSULATED EXHAUST PIPE AND METHOD AND MEANS

FOR PRODUCING AND CONNECTING SAME

Field of the Invention

This invention relates to insulated pipe. More particularly, it relates to insulated pipe adapted for use in the exhaust system of a vehicle powered by an internal combustion engine. The invention further relates to apparatus and method for manufacturing such pipe and to means for attaching the exhaust pipe to an engine manifold or other element in an automotive exhaust system.

Background of the Invention

Catalytic converters are conventionally included in the exhaust system of automotive vehicles to reduce the level of pollutants discharged to the air. While it is generally believed that the catalytic converters used today perform satisfactorily once their light-off temperature is reached, a pollution problem exists during the light-off period. For example, it has been determined that 90% of the pollutants exhausted to the atmosphere from an exhaust system which includes a catalytic converter are formed during the light- off period. As used herein, the light-off temperature is the temperature at which a catalytic converter catalyzes the reaction that takes place in the converter with the exhaust gases. The catalytic light-off period is the time required for the catalytic converter to reach its light-off temperature.

If the heat of the exhaust gases, which can reach temperatures as high as 1800 °F in turbo-charged automobiles, can be retained for a longer period of time than in conventional exhaust systems, the time required for the light-off temperature to be reached will be reduced. This would then reduce the duration of high pollution, and in turn reduce the amount of pollutants released to the atmosphere.

Attempts have been made in the past to develop insulated "exhaust systems. Double exhaust pipes have been suggested, comprising spaced inner and outer pipes. Although this**reduces the amount of heat loss, it is not enough t© appreciably retain heat at the level required for optimum catalytic converter operation.

Another suggestion is found in U.S. Patent No. 4,345,430* ? issued to Pallo et al. In that patent a double* pipe system comprised of inner and outer corrugated metal tubes is disclosed. In addition, the use of insulation between the inner and outer tubes is suggested. Various types of insulation materials capable of withstanding temperatures up to 1600°F are suggested in the patent. At the temperature requirements of modern automobiles and catalytic converters, however, refractory fiber insulation is the most practical choice of insulation .to-be used.

Although refractory fiber is capable of resisting the high temperatures to which it would be exposed and providing :he necessary degree of insulation, it is a very fragile material. When used in an insulated exhaust system s-uch as that disclosed in U.S. Patent No. 4,345,430, wherein the insulated pipe is used as a structurally .independent unit in place of the conventional type of exhaust pipe, it was found that the physical stresses to which it was exposed during use caused it $_p be reduced to small dust-like particles. In this condition it was no longer able to provide satisfactory insulation. Obviously, if refractory fibers are to be used in an insulated exhaust system of this type, they must be be capable of resisting degradation.

Moreover, a manufacturing process must be found to efficiently produce a length of double pipe which has refractory fiber insulation in the space between the pipes. This problem was addressed in U.S. Patent No. 4,345,430,...but the proposed solution was not found to be practical. It was suggested to form a first relatively small tubes of spirally wound corrugated metal and to spirally wind a layer of refractory fiber felt onto the tube. To encase the insulated tube in another larger tube, it was suggested to spirally wind a second corrugated metal tube directly over the insulated tube. This method is too difficult to regulate, and the required machinery to carry it out is too complicated and expensive. Excessive pressure on the felt as it is being wound about the corrugated tube tends to tear the felt, and it is difficult to precisely wind the felt so as to avoid overlaps and gaps between windings. Further, maximum efficiency in producing the outer corrugated tube cannot be attained by winding adjacent corrugated strips about a previously formed insulated pipe while at the same time forming seams from the adjacent edges of the strips. A much simpler and more reliable method of manufacture is needed for the commercial production of an insulated exhaust pipe.

A further problem posed by corrugated exhaust pipe structure of the type discussed is the difficulty in attaching it to the manifold or other elements of the exhaust system. The fragile nature of the refractory fiber insulation and the relatively thin corrugated metal tubing give the pipe little resistance to crushing or deformation by clamps designed to hold the ends of the pipe in place through the application of high pressures. As pointed out above, if the pipe is not securely held in place the vibration to which it is subjected in time degrades the refractory fibers. Further, the attachment should' prevent the escape of gases from the inner tube into the insulation. This can readily occur at the end of the pipe, resulting in the outer pipe being exposed to the hot exhaust gases and increasing the heat loss from the exhaust pipe.

It is thus an object of the invention to provide an exhaust pipe attachment means which does not damage the pipe or the insulation but nevertheless holds the pipe securely in place against vibration. It is also an object to prevent exhaust gases from entering the insulation at the end of the pipe. As an alternative to insulating an automotive exhaust system by substituting specially designed insulated pipe for the exhaust pipe normally employed, it would be desirable in some cases to be able to insulate the conventional exhaust pipe of a vehicle in place. This would make it more feasible to insulate sections of the exhaust pipe other than the section connecting the exhaust manifold and the catalytic converter so as to function as a heat shield and to absorb exhaust system noise. The substitution of insulated exhaust pipe for conventional- exhaust pipe in order to accomplish this objective Srould not normally be recommended since it would be quite expensive, and the resulting insulated pipe would still not be as strong as conventional exhaust pipe.

It would therefore be highly desirable to be able to insulate conventional automotive exhaust pipe in a simple, inexpensive manner, including the ability to insulate curved, angled and dimpled portions of the exhaust pipe as well as straight portions. A related problem which arises in an automotive exhaust system is caused by the torque created by the engine during periods of acceleration and deceleration. For engines which are aligned so that the crankshaft extends along the length of the vehicle, conventional connections between the engine manifold and the exhaust system are able to absorb the torque -without problems. For engines arranged along a transverse axis, however, the torque stresses the normally rigid connection between the engine manifold and the exhaust system, which can eventually cause fatigue cracking of the engine manifold.

To prevent the transmission of torque forces to the engine manifold, it is necessary to replace the normally rigid ' o ne tion between the engine manifold and the exhaust system with one that does not transmit the torque forces. 'This typically has been accomplished through use of a ball-*- and socket joint, which allows the angle between the manifold and the exhaust system to vary without transmitting undesirable stresses to the engine manifold. Although this arrangement has been successful in preventing fatigue cracking of the manifold, the joint is not able to contain the exhaust gases, allowing them to leak out into the atmosphere without passing through the catalytic converter. This creates the potential danger of leaked exhaust gases entering the passenger compartment of the vehicle.

Further drawbacks in conventional coupling arrangements are the lack of thermal insulation in the connection between the engine manifold and the exhaust system and the high cost of such connectors.

It would therfore be desirable to be able to unload the engine manifold from exhaust system torque in a more reliable and efficient manner, and to do so at a more economical cost.

Summary of the Invention

In accordance with one aspect of the invention an insulated pipe for use in the exhaust system of a vehicle powered by an internal combustion engine comprises spaced concentrically arranged inner and outer metallic tubes, with refractory fiber insulation filling the space between the tubes. A major portion of the insulation is relatively low density refractory fiber insulation, while a minor portion is relatively high density refractory fiber strips extending along the length of the pipe. The high density strips inhibit movement of the low density fiber to prevent degradation of the low density fiber during operation of the vehicle. The strips preferably comprise a plurality of circumferentially spaced strips, the thickness of which is greater than half the radial thickness of the space between tubes. The density of the low density insulation is in the range of 4 pcf to 16 pcf, which allows the insulation material to be flexible enough to wrap around the pipe. The high density insulation is in the range of 24 pcf to 28 pcf, providing enough body and strength to resist the stresses to which the unit is subjected and also to hold the low density 6 fibers in place against the forces of vibration.

In an@ther aspect of the invention the insulated pipe is manufactured by introducing a layer of refractory fiber insulation to a work station, adhering the insulation to the periphery of the small diameter tube and then inserting the insulated tube into the larger diameter tube so that the layer of insulation is in contact with the second tube. The step of adhering the insulation layer to the small tube is carried out by rolling the tube, after having first applied adhesive to the insulation or to the tube, over the insulation to hold the insulation in place. The insulation is introduced to the rolling station by pulling a length of it from a roll onto the conveyor that carried it to the station.

The larger tube is a spirally wound corrugated metallic" tube wh-ch is caused to have relative reciprocal movement toward the insulated smaller tube. The insulated 'smaller tube is rotated with respect to the larger tube,so that the speed of the relative rotation is coordinated to the speed of the relative reciprocal movement to cause the insulated tube to be threaded into the corrugations of the larger tube without damaging the fibrous insulation.

In order to attach insulated corrugated exhaust pipe to an element, such as the manifold, in the exhaust system, an attachment conduit is provided which is attached at one end to the element. The other end of the attachment conduit extends into an end of the inner corrugated metallic tube of the insulated pipe. The conduit includes means extending transversely therefrom which engages at least one corrugation of the inner metallic tube to assist in holding the insulated pipe in place. Because the corrugated tube is formed from a spirally wound corrugated metal strip, the corrugations extend at an angle to the axis of the pipe. The transversely extending means on the conduit are also aligned at an angle corresponding to the angle of the corrugations , enabling the conduit to be threaded into the pipe . Preferably, the transversely extending means are lugs comprising ears stamped from the ends of the conduit .

In addition , a cap is slidably mounted on the conduit so that the end of the exhaust pipe is received between the cap and the conduit. This allows the conduit to be freely threaded into the exhaust pipe . A stop on the conduit is provided to stop the sliding movement of the cap to allow the conduit to be tightly secured to the exhaust pipe. The end of the exhaust pipe would thus be tightly pressed against the end of the cap.

In accordance with the aspect of the invention involving the insulating of an existing conventional exhaust pipe , an insulated tube is provided which is capable of being trained over the exhaust pipe of a vehicle, including the angled or curved portions thereof . The insulated tube comprises an inner metallic tube having a slightly greater diameter than that of the exhaust pipe , and an outer metallic tube of greater diameter than that of the inner metallic tube. The outer tube is radially spaced from the inner tube , and insulation which is capable of withstanding the high temperatures of the exhaust gases fills the annulus between the inner and outer tubes.

Means are further provided for permitting the insulated tube to be trained over the angled portions of the automotive exhaust pipe . In the pref erred embodiment , this is accomplished by providing the inner and outer tubes with corrugations having a wall thickness of only approximately 0 .002 inch to 0. 004 inch . This results in a very lightweight inexpensive insulated tube which can be trained over an existing exhaust pipe, thus obviating any need to replace the exhaust pipe . This approach retains the structural integrity of the original exhaust pipe while allowing the pipe to be insulated in a simple economic manner . The means for holding the insulated tube in place can be of simple design because there is no need for special design features to enable it to be moved tranversely into place on the exhaust pipe. Instead, as indicated above, the insulated tube may simply be slid along or trained over the length of the exhaust pipe, regardless of its contour.

The invention further comprises a flexible coupling which is capable, with respect to the transmission of torque forces, of decoupling the engine manifold and the exhaust pipe system in an automotive vehicle. The coupling comprises a flexible metal tube which has an inlet tube extending through one end and an outlet tube extending through the other end. The inlet and outlet tubes comprise portions of an exhaust gas flow path through the coupling and have interior ends located within the coupling. Means are provided for connecting the en s -of the flexible metal tube to the inlet and outlet tubes. The interior ends of the inlet and outlet tubes are arranged so as to be capable of substantial angular movement relative to each other upon bending of the flexible metal tube. Thus, forces which tend to cause angular movement between the engine manifold and the exhaust system are taken up by the flexible coupling instead of being transmitted to the engine manifold.

The coupling may be insulated by insulating the exterior of the flexible metal tube and providing a second*" lexible metal tube to hold the insulation in place. The flexible tubes may be connected to the inlet and outlet tubes in the manner described in the more detailed description hereinafter so as to provide a gas- tight coupling which effectively prevents the escape of exhaust gas-s¬ in a preferred arrangement, the inlet and outlet tubes have enlarged upstream portions, enabling the enlarged portion of the outlet tube to overlap either the downstream end of the inlet tube or the downstream end of an intermediate tube length of similar shape positioned within the inner flexible metal tube. This overlapping arrangement, while maintaining sufficient clearance between the inner flexible metal tube and the inlet and outlet tubes and any intermediate tube, permits the necessary relative angular movement between the inlet and outlet tubes.

Other features and aspects of the invention, as well as other benefits thereof, will readily be ascertained from the more detailed description of the preferred embodiments which follows.

Brief Description of the Drawings

FIG. 1 is a pictorial view of the structurally independent insulated exhaust pipe of the invention, with portions of the elements thereof being broken away to better expose its structure;

FIG. 2 is a transverse sectional view taken on line 2-2 of FIG. 1;

FIG. 3 is an enlarged transverse sectional view of a corrugated metal strip used to form the corrugated exhaust tubes which form the structurally independent exhaust pipe;

FIG. 4 is an enlarged transverse sectional view of the seam between adjacent strips in a corrugated tube;

FIG. 5 is a pictorial view of the apparatus for wrapping insulation around the inner tube of the exhaust pipe of FIG. 1;

FIG. 5A is a partial pictorial view showing a modified form of the insulation feeding means of FIG. 5;

FIG. 6 is a transverse sectional view of the insulation being fed to the wrapping apparatus, taken along line 6-6 of FIG. 5;

FIGS. 7A, 7B and 7C are schematic side elevations of the wrapping apparatus of FIG. 5, showing the apparatus in sequential stages of operation;

FIG. 8 is an end view of the apparatus of FIG. 5, showing the wrapping operation;

FIG. 9 is an enlarged end view of the tube feeding means shown in FIG. 8;

FIG. 10 is a view similar to that of FIG. 9, but showing the apparatus at a later phase of its operation; FIG. -Jfel is a pictorial view of the apparatus for inserting an insulated tube into a larger tube in the manufacture of the exhaust pipe of FIG. 1;

FIG. 12 is an enlarged partial transverse sectional view showing the movement of an insulated tube into a larger tube in the manufacture of the exhaust pipe of FIG. l;

FIG. 13 is an exploded pictorial view of the attachment means of the invention for attaching a corrugated?; exhaust pipe to an element in the exhaust systep; , . * ,s

FIG. 14 is n end view of the attachment means of FIG. 13, with the slidable cap shown mounted on the attacφment*conduit;

FIG. 15 is an enlarged partial sectional view showing, the attachment means of FIG. 13 in the initial stage of 'being threaded into the end portion of an exhaust.pipe * „

FCG. 16 is an enlarged partial sectional view showing the attachment means of FIG. 13 after it has been if** fully threaded intothe end portion of an exhaust pipe;

FIG. 17-*is a transverse sectional view showing the attachment means of FIG. 13 connected to the manifold of an automotive engine;

FIG. 18 is a partial side view showing a modified mounting flange arrangement;

FIG. 19 is a pictorial view of a modified attachment tube;

FIG. 20 is a front elevational view of the modified attachment tube of FIG. 19;

FIG. 21 is a schematic view of an automotive exhaust system incorporating the insulated tube of the present invention d-f the type designed to be trained over an existing conventional automotive exhaust pipe;

•fe . . .

FIG. ' 22 is a partial pictorial view of a conventional automotive exhaust pipe over which the insulated tube of FIG. 21 has been trained, parts of the elements of the tμbe being broken away for the sake of clarity;

FIG. 23 is a transverse sectional view taken along line 23-23 of FIG. 22;

FIG. 24 is a partial pictorial view of the insulated tube of FIG. 22 positioned on an angled portion of the exhaust pipe;

FIG. 25 is an enlarged partial side elevation of the insulated tube of FIG. 22, showing means for enclosing the insulation at the end of the tube;

FIG. 26 is an enlarged partial side elevation similar to the view of FIG. 25, but showing another embodiment for enclosing the insulation at the end of the tube;

FIG. 27 is a schematic view of a portion of an automotive exhaust system incorporating the coupling of the present invention for relieving the manifold of engine torque stresses;

FIG. 28 is an enlarged side elevation of the portion of FIG. 27 enclosed within the circle 28;

FIG. 29 is an enlarged longitudinal sectional view of the coupling taken along line 29-29 of FIG. 28;

FIG. 30 is a transverse sectional view of the coupling taken along line 30-30 of FIG. 29;

FIG. 31 is a transverse sectional view of the coupling taken along line 31-31 of FIG. 29;

FIG. 32 is an enlarged transverse sectional view of the corrugated strip enclosed in the circle 32 in FIG. 29;

FIG. 33 is a longitudinal sectional view similar to that of FIG. 29, but showing the coupling in flexed condition;

FIG. 34 is a partial longitudinal sectional view similar to that of FIG. 29, but showing a modified arrangement;

FIG. 35 is a longitudinal sectional view similar to that of FIG. 34, but showing the coupling in flexed condition; and

FIG. 36 is a partial longitudinal sectional view similar to that of FIG. 34, but showing another modified arrangement.

Description of the Preferred Embodiments

Referring to FIGS. 1 and 2, the exhaust pipe 10 of the invention comprises an inner corrugated metal tube 12, an outer corrugated metal tube 14 and a layer of refractory fiber insulation 16 between the tubes. The insulation 16 completely fills the space between the tubes 12 and 14 and further contains spaced longitudinal refractory fiber strips 18 extending radially from the inner tube 12 for a distance greater than half the radial thickness of the space between the tubes. Preferably, in accordance with the method of fabricating the exhaust pipe, the insulation 16 and the strips 18 are adhered to the inner tube 12 by a coating or layer of adhesive 19.

The insulation 16 comprises refractory fibers because they are capable of withstanding the high temperatures of exhaust gases from automotive engines and because the material is lightweight. The fibers are preferably provided in the form of blankets for ease of handling and to meet the demands of the pipe fabrication process. Various grades of refractory fiber blankets are commercially available, depending on the temperatures to which the insulation will be exposed in operation. Cerawool Blanket for service up to 1600°F, Cerablanket for service up to 2400°F, and Cerachem and Cerachrome Blankets for service up to 2600°F are all available from Manville Sales Corporation and will function well in the insulated pipe., of the invention. Refractory fiber blankets such as these are formed from very pure alumina, silica and other refractory oxides, a typical general formulation **being 40% to 60% by weight of silica, 40% to

60% by weight of alumina and 0 to 10% by weight of oxides such as chromia, iron oxide, calcia, magnesia, soda, potassia, titania, boria or mixtures of these oxides. The insulation is able to retain a soft fibrous structure at elevated temperatures and can be needled together for higher mechanical strength. It has low thermal conductivity and low shrinkage, and also provides good sound absorption. Because of their resilient and flexible nature such blankets in a density range of 4 pcf to 16 pcf can readily be wrapped around a pipe. Fibrous insulation material such as fiber glass or mineral wool could not stand up to the high temperatures of the gases coming from the manifold of modern vehicles.

Although refractory fiber material of the type discussed above has previously been proposed as an insulating material to be used in an insulated exhaust pipe for an automotive exhaust system, it was found in practice that the insulating properties of the pipe decreased drastically after a period of use. This was surprising in view of the beneficial properties of the refractory fiber. It was found, however, that even though refractory fiber is soft and resilient, it nevertheless is a very fragile material, disposed to degradation under the conditions encountered in automotive use. Specifically, it was found that the vibration to which it was subjected in the normal operation of a vehicle on which structurally independent insulated pipe was mounted was sufficient to reduce the fiber to dust-like particles. Since the low density refractory fiber insulation performed well in all other respects it was preferable to find a way to protect it from the effects of vibration rather than search for a different, probably more expensive, insulating material.

It was found, surprisingly, that the use of spaced strips of higher density refractory fiber insulation functions to hold the low density insulation in place and to protect it against vibration. The number of strips and their placement obviously may vary, depending upon the dimensions of the pipe. Although higher density insulation performs well at higher temperatures, the lower density insulation blanket 16 is required for its ability to be wrapped about the inner tube 12 and for its better overall insulating performance under wider ranges of temperature. Therefore, the size of the strips will 14 be kept relatively small compared to the volume of low density insulation. It is further preferred that the strips be equally spaced about the periphery of the inner tube for best functioning. While in some circumstances only two stri s" may be utilized, it has been found that three equalUy spaced strips provide adequate protection to the lower density insulation while at the same time being present in such minor amounts that the insulating value of the lofr density insulation is not noticeably changed- In order to provide their reinforcing and stabilizing functions, the strips 18 should extend from the inner tube, as mentioned previously, at least half the radial thickness of the space between the tubes 12 and 14. I j, is preferred that they stop short of the outer tube 14 in order to avoid direct contact with the outer tube and in order to avoid fabrication problems which such an' arrangement might create. The density of the strips is greater than the density of the lower density- insulation and preferably is in the range of 24 pcf to 28 pcf. This provides the strips with the properties and qualities needed but leaves them with sufficient flexibility to withstand the fabrication process.

The tubes 12 and 14 are preferably corrugated in order to give the pipe the flexibility needed for installation onbvarious types of vehicles and at various angles. The thickness of the tubes should preferably be in the range of about 0.005 inch to 0.010 inch. If the pipe thickness i& less than this amount it will not have enough strength to resist fatigue and very likely will eventually, break. If the thickness is greater than this amount -it will not have sufficient elongation or malleability to enable the seam between adjacent corrugated strips to be formed during formation of the tubes. This very thin structure substantially reduces the weight of the insulated pipe, with the benefit that the resulting low thermal mass reduces the amount of heat loss ■and thus> reduces the time for the catalytic converter to reach its light-off temperature. The tubes are spaced from each other over their entire length, thus avoiding metal-to-metal contact. This is important because it eliminates areas of greater heat loss and it also acts to isolate exhaust noise.

Referring to FIG. 3, the tubes are formed from a strip of corrugated metal, such as the strip illustrated at 20, by feeding it to a forming roller and mandrel at a predetermined angle to the mandrel in accordance with well known procedures. Such a process, which is described in more detail in U.S. Patent No. 3,753,363 to Trihey, results in the corrugations of the finished tube extending at an angle to the length of the tube equal to the angle at which the corrugated strip was fed to the mandrel. Such a strip contains a number of parallel corrugations 22 the formation of which by a series of corrugating rollers is well known. Although any suitable seam may be used to connect adjacent strips in forming a corrugated pipe or tube, for purpose of illustration the strip 20 is shown with one edge having a large flange 24 and the other edge having a smaller flange 26. As shown at the right side of FIG. 3, the small flange 26 of one strip fits into the large flange 24 of the adjacent strip. The nested flanges are then subjected to a crushing operation, as is well known in the art, to produce the gas-tight seam 28 shown in FIG. 4, wherein the flat side of the seam corresponds to the inside of the tube. Although the dimensions of the exhaust pipe of the invention will vary according to the specific end use of the pipe, a typical automotive exhaust pipe would have an inner diameter of two inches, with a pitch or on- center spacing of the corrugations of 0.16 inch.

Referring now to FIG. 5, which illustrates the preferred apparatus for wrapping the inner corrugated tube with the refractory fiber insulation, a continuous layer of insulation is pulled from a roll 30 by conveyor 32. The roll 30 is freely mounted for rotation on a shaft 34 resting on suitable supports 36. The insulation rests on the conveyor 32 and is able to be moved by the conveyor belt due to the friction between the insulation strip and the belt. The roll may be provided at the refractory *fiber manufacturing plant with a plurality of spaced high density refractory fiber strips 18. Alternatively, as illustrated in FIG. 5A, the roll may consist only of the low density refractory fiber layer 16, and the high density strips 18 may be fed onto the layer from separate rolls 38 of the strips at a point above the conveyor 32. In either case, the layer of low density irisulation 16, with strips 18 resting on the upper surface thereof, appears as shown in FIG. 6 during travel on the conveyor 32.

Referring back to FIG. 5, a second conveyor is spaced a short distance downstream from the end of the first conveyor 32. Located between the conveyors above the gap between them is a shear 42 connected to a power cylinder 44 for moving the shear downwardly in a cutting stroke and back.up again to its original position. Immediately downstream from the shear are adhesive spray nozzles 46 positioned above the path of travel of the insulation. Downstream from the spray nozzles is a series of laterally oriented endless belts 48. The belts are trained about rolls 50 mounted on shafts 52 and 54, with one of the shafts being rotated to cause all the belts to move at the same time. The shafts are supported in vertical support frame members 56 connected to upper horizontal supports 58, and the entire frame is movable by means of cylinders 60 connected to each horizontal support 58. Any suitable arrangement for rotating the shafts 52 and 54 may be employed, such as the arrangement illustrated wherein motor 62 is also supported on one of the supports 60 and rotates the shaft 52 through a belt 64 and a gear 66 mounted on the end of an extension 68 of the shaft 2

Located adjacent the series of belts 48 and adjacent one side of. the conveyor belt 40 is a tube support rack consisting"of spaced inclined ribs or slats 70 on which a supply of the smaller corrugated tubes 12 is supported. Located adjacent the other side of the conveyor belt 40 is a bin consisting of a sloped support shelf 72 and a vertical shoulder 74 for supporting the tubes 12 after they have been wrapped with insulation.

In operation, starting from the position of the insulation shown in FIGS. 5 and 7A, wherein the downstream end of the insulation is resting on the conveyor 40 just beyond the junction between the conveyors 32 and 40 and is slightly upstream from the spray nozzles 46, the conveyors 32 and 40 are actuated. The conveyors pull the insulation, unwinding it from the roll 30 and moving it downstream on the conveyor 40. A photo-electric switch, not shown, actuates the spray nozzles when the insulation moves beneath them. Adhesive is continuously sprayed onto the insulation as it moves downstream. When the insulation reaches the point shown in FIG. 7B, where the distance from the downstream end of the insulation to the shear 46 is almost equal to the desired length of insulation, another photo-electric switch actuates the cylinder 44 which swiftly moves the shear 42 through its cutting stroke while the web of insulation is still moving. After a slight delay, to allow the upstream end of the insulation to reach the spray nozzles, the adhesive spray is shut off and the conveyor 32 is stopped. The conveyor 40 continues to operate, moving the web of insulation downstream until a third photo-electric switch located adjacent the last endless belt 48 shuts off the conveyor 40. The insulation is now in the position shown in FIG. 7C, wherein it is laterally aligned with the series of endless belts 48, with its upstream end being spaced from the downstream end of the insulation still attached to the roll 30.

Referring now to FIG. 8 as well as to FIG. 5, at this point the endless belts 48 are actuated, as is the cylinder 76. The cylinder 76 pushes up tube support 78 which prior to being moved functioned as the lowermost portion of the tube support rack 70. This raises the tube 12 supported thereon to the point shown in FIG. 9, at which time the combination of the inclined support surface- 78 *and contact between the tube and the moving belts 48 moves the tube onto the insulation 16. The other tubes in the rack 70 do not interfere with the movement of* the support 78 due to the guard 80 extending down from the support, which prevents the tubes in the rack from rolling down until the support 78 has been returned to its original position as shown in FIG. 10. As depicted- in FIGS. 8 and 10, continued movement of the belts 48*rolls the tube over the adhesive-coated surface of the insulation, causing the insulation to adhere to the tube and to be wrapped around it as the tube is rolled by the belts 48 toward the bin 72.

Still referring to FIGS. 5, 8, 9 and 10, and particularly to FIGS. 9 and 10, it will be noted that as a tube *T2* is wrapped with insulation its effective diameter increases. Thus if the height of the endless belts 48 is set- in order to begin rolling the tube over the layex of insulation, it will soon be too low to continue rolling the combined tube and insulation. For this reason the cylinders 60 function to raise the belt support frame 56, 58 at the appropriate time to compensate for the increased diameter of the insulated tube. It will be understood that the cylinders 60 can also -be used to raise or lower the frame to allow tubes of different diameters to be wrapped.

Referring now to FIG. 11, in order to insert the insulated tube resulting from the wrapping operation into the larger tube the apparatus 82 is employed. This comprises an elongated clamp 84 mounted on a carriage 86 which in turn is mounted for operative engagement with a screw 88 driven by motor 89 through drive belt 91. The clamp includes a lower element 90 of half-cylindrical shape hinged to an upper element 92, also of half- cylindrical shape. One end of the clamp is closed as at the end walls 94 and 96 of the clamp halves 92 and 90. The other end is open to allow insertion of an insulated tube.

The other part of the tube insertion or stuffing mechanism is a mandrel assembly 98 consisting of mandrel 100 aligned with the clamp 84. The mandrel is mounted in a support bearing 102 which is connected by shaft 104 and drive pulley 106 to motor 108 for rotation thereby. The entire bearing mounting 102 is itself mounted on a pivoting base 110 connected by arm 112 to cylinder 114. Actuation of the cylinder 114 pivots the mandrel assembly to the dotted line position to allow an insulated tube to be loaded onto the mandrel.

In operation, a large diameter corrugated tube is inserted into the bottom half 90 of the tube clamp 84 and the upper half 92 is closed. A suitable latch mechanism, not shown, for holding the clamp shut would be provided. An insulated small diameter corrugated tube is slipped over the mandrel 100. The dimensions of the clamp and mandrel are designed to receive the tubes so that the larger tube is tightly held in the clamp while the smaller insulated tube is slidably fitted on the mandrel. The mandrel is then rotated by the motor 108, and the screw 88 is rotated by the motor 89. This causes the carriage 86 and the clamp 84 supported thereon to move toward the mandrel 100. The mandrel and the insulated tube 12 carried by the mandrel will thus move into the clamp 84 and into the outer tube 14 held in the clamp. When the mandrel has reached the desired position within the clamp, the screw carriage 86 contacts limit switch 116, causing the motor 89 to be reversed to move the clamp 84 back toward its starting position, thereby withdrawing the clamp and the insulated tube from the mandrel. When the carriage 86 reaches the limit switch 118 the motor 89 is stopped, halting the travel of the carriage and clamp. In addition, the limit switch 118 activates the cylinder 114 to pivot the mandrel 100 to its dotted line position for reloading. Contact of limit switch 120 by arm 122 carried by the pivoting base 110 of the mandrel assembly causes the cylinder to stop pivoting the mandrel 100. After the clamp and mandrel have again been loaded; with tubes a switch to pivot the mandrel base assembly back to its operative position would be actuated by hand. The mandrel would stop at the appropriate time to be once again aligned with the centerline of the clamp by the arm 122 contacting another limit switch 124 and causing the.cylinder 114 to be deactuated.

As best .shown in FIG. 12, while the clamp 84 is moving the outer corrugated tube 14 toward the mandrel 100 the mandrel is being rotated. The direction of rotation is in the same direction as the inclination of the corrugations in the inside diameter of the tube 14, and the spfesed ®~ζ> rotation of the mandrel is correlated with the speed of axial movement of the carriage and clamp so that the insulation 16 is effectively screwed into the outer tube 14, with the corrugations of the tube 14 acting as threads. This prevents the insulation from becoming damaged, as could happen if it were pushed or forced into the tube 14 without the threading action, and permits a tight fit of the insulation between the inner and outer taibes. The insulation thus extends completely from the inner tube to the outer tube, preventing metal- to-metal contact between the inner and outer tubes.

It will be understood by those skilled in the art that the sequence and speed of the various operations described in the manufacture of the exhaust pipe can readily be* controlled by any of a number of available relatively simple computer programs.

It will now be appreciated from the foregoing description that the insulated pipe of the present invention is a simple, effective and economical solution to the problem of how to retain the heat from exhaust gases prior to the gases reaching the catalytic converter, * The method and apparatus for manufacturing the pipe is simple yet highly effective in being able to produce the pipe on a production line basis while maintaining the necessary quality control. The exhaust pipe attachment means of the present invention is designed to be used in connection with an insulated exhaust pipe of the type described above, wherein the corrugated tube walls are typically quite thin, in the range of 0.005 inch to 0.010 inch. Because refractory fibers are very fragile, the clamping attachment to the exhaust system must hold the pipe firmly in place to prevent undue vibration that can cause the fibers to be reduced to dust-like particles. Even when using a pipe such as that shown in FIG. 1, wherein spacer strips 16 of higher density refractory fiber are embedded in the low density fiber layer to hold the low density fibers in place as a preventive measure against the effects of vibration, it is still essential that the pipe attachment hold the pipe solidly in place. Moreover, the clamp cannot be made so tight that the tube ends are squeezed together, as this could result in metal-to-metal contact, which is detrimental to the heat and sound insulating properties of the pipe, and could also result in crushing the fibers, thereby destroying much of their insulating value at that location.

Referring to FIGS. 13 and 14, the exhaust pipe attachment of the invention comprises a conduit 130 welded at one end, as at 132, to a mounting flange 134. The mounting flange contains three equally spaced elongated bolt holes 136 to facilitate mounting the assembly to a manifold or other element in an automotive exhaust system. At the other end of the conduit tabs 138 have been stuck from the conduit end for a purpose to be explained hereinafter. Spaced from the tabs is a circumferential protrusion 140 which acts as a stop for cap 142. The cap 142 comprises an end wall 144 containing an opening 146 through which the conduit fits. The opening is large enough to allow the cap to slide on the conduit but is smaller than the protrusion 140. Extending axially of the conduit and spaced therefrom is a sleeve portion 148. The sleeve portion is thus concentrically arranged with respect to the conduit and forms with the conduit an annular space 150.

Turning now to FIG. 15, to install the attachment to a corrugated insulated exhaust pipe comprising a corrugated'metal inner tube 152, a corrugated metal outer tube 154 and a layer of insulation 156 in the annular space between the corrugated tubes, the end of the conduit 130 containing the tabs 138 is aligned with the exhaust pipe so that the pipe fits into the annular space between the conduit 130 and the sleeve portion 148 of the cap. Thβj conduit is then rotated in a direction corresponding to the alignment of the corrugations of the pipe. Thus the conduit 130 is rotated so that each of the tabs 138 engages a corrugation on the inside diameter of the inner tube 152. Rotation of the conduit will then cause the engagement of the tabs and corrugations to have a threading action, resulting in the exhaust pipe being drawn toward the mounting flange. Because the cap 142 is slidably mounted on the conduit 130, the drawing of the pipe toward the mounting flange results in the end of the pipe pushing the -cap to slide it along the conduit in the same direction. The initial stage of such a threading action is illustrated in FIG. 15.

Continued rotation of the conduit 130 causes the conduit to-move into the exhaust pipe until the cap 142 is pushed ^against the protrusion 140. The protrusion thus acts as a stop to the threading action. When this occurs the conduit is turned still more to apply a torque to the conduit to secure the end of the pipe tightly against, the end wall 144 of the cap. This final stage of the threading action is illustrated in FIG. 16. Preferably^ a coating 158 of ceramic adhesive is first applied to the end wall 144 to act as a seal or gasket to further assure against the escape of exhaust gases into the fibrous insulation 156.

To provide for.-the threading action to take place it is necessary to align the tabs 138 at an angle to the axis of th attachment which corresponds to the angle of the corrugations of the inside diameter of the inner pipe or tube 152. Obviously, the angle will be the same as the angle at which the corrugated strip used to form the corrugated tube 152 has been fed to the axis of the forming mandrel. While this may vary, an angle of 20° from a plane extending at right angles through the axis of the conduit 130 would be typical.

Although the tabs 138 have been described as being formed by striking them from the end of the conduit 130, this method is just one way in which they may be provided. Any transversely extending lugs lying at the proper angle would perform the same function, regardless of whether they are an integral part of the conduit, as the struck tabs would be, or are separate extensions affixed, as by welding, to the conduit. Although two tabs have been disclosed as the preferred arrangement due to the ease with which the threading operation can be carried out and for the holding power they provide, the number of tabs or lugs is not limited to two. One or even three or more lugs may be used as long as the desired function is provided.

The protrusion 140 in the conduit 130 has been described as circumferential or annular. This is the preferred arrangement because it can readily be formed by stamping a groove in the inside diameter of the conduit which results in a bulge or protrusion on the outside diameter. Any form of stop means can be used, however, as long as it is strong enough to withstand the pressure of the end cap being pushed against it due to the torque applied during the attachment operation. For example, tabs could be struck up from the conduit wall at spaced peripheral locations, or separate stop members could be welded to the conduit.

Once the attachment has been permanently secured in place the mounting flange can be aligned with the mounting holes in the exhaust system element to which the exhaust pipe is to be attached, and the mounting flange can be bolted to the element. Thus in FIG. 17 the pipe attachment is shown bolted to the attachment flange 160 of the engine manifold of an automotive engine . The three bolt holes 136 provided in the mounting flange 134 make it possible for them to be aligned with the holes in the attachment flange 160 with only a small amount of rotation of the attachment means being required. The exhaust pipe can readily absorb this degree of torque or stress during installation due to its helical corrugated des ign . This~ would not be poss ible with the more conventional * solid or welded bellows type of exhaust pipe . Because the pipe design makes it possible to use a flat mounting flange such as that shown at 134 , a smaller amount of space- is taken up on installation, resulting in a greater portion of the length of the exhaust pipe system bei g insulated.

As shown in FIG. 18 , a different mounting flange arrangement can be - used if it is desired to apply less torque to ithe pipe when attaching it to the manifold or other element' in the exhaust system. The flange 162 is slidably mounted on the conduit 130 and is used in conjunction with a flared portion 164 on the end of the conduit . This enables the mounting flange 162 to be rotated to align the mounting holes 166 with the mounting holes in' the attachment flange of the manifold or other element . While this design has the advantage of lessening,. the stress on the exhaust pipe during mounting, it has thS disadvantage of requiring more space for maneuvering during the mounting operation , requiring the length of the conduit between the mounting flange and the annular stop to be increased, thereby resulting in less of the exhaust pipe system being insulated.

If des ired , a vari ation o f the exhaus t p ipe attachment may be used such as that shown in FIGS . 19 and 20 , wherein like reference numerals to those of FIG . 13 denote like elements . In this embodiment the tube 130 / does not have a straight-cut end with tabs but is provided instead with a helical end portion 168. The side edges^ of a notch or cutout 170 in the end of the tube 13-&' allow for the end of the tube to be helically shaped, the helical end portion beginning at the short side edge 172 and ending at the long side edge 174. The helical end portion 168 is formed with a rim or flange 176 which engages with the corrugations on the inside diameter of the inner tube of an insulated exhaust pipe to thread the attachment and pipe toward the mounting flange as in the embodiment of FIG. 13. The helical end portion provides greater surface contact with the corrugations than the tabs of the embodiment of FIG. 13 and can exert more force on the tube during the mounting operation.

As previously mentioned, instead of utilizing a self-supporting insulated exhaust pipe as described in connection with FIGS. 1-12, the present invention also contemplates an insulated tube which is designed to be slid or trained over a standard exhaust pipe section. Referring to FIG. 21, an automotive exhaust system 180 is illustrated schematically as comprising internal combustion engine 182, exhaust manifold 184, and an exhaust pipe section 186 connecting the manifold and catalytic converter 188. Another exhaust pipe section 190 connects the catalytic converter 188 to muffler 192, and a further section 194 connects the muffler 192 to resonator 196. A tail pipe section 28 extends from the resonator 26. Each of the exhaust pipe sections includes at least one angled or curved section, which is typical of automotive exhaust pipe installations, and each pipe section is jacketed by the insulated tube 200 of the present invention.

Referring to FIGS. 22 and 23, exhaust pipe 202, which may be the exhaust pipe of any of the sections 186, 190 and 194, is jacketed by the insulated tube 200. The insulated tube 200 comprises spaced inner and outer corrugated tubes 204 and 206, with the annulus between the tubes being filled by a layer of insulation 208. The inner and outer corrugated tubes 204 and 206 may be fabricated in any convenient way, as by the known method previously referred to of feeding a corrugated strip of metal to a forming roller and mandrel at a predetermined angle to the mandrel, with the corrugations of the resulting helically wound tube extending at an angle to the length* of the tube equal to the angle at which the corrugated strip was fed to the mandrel. The ends of the corrugated strips would have flanges which, as described above, are nested in the adjacent flange and compressed to form a gas-tight seam.

Although the finished insulated tube is preferably formed by^ a method similar to that described in connection with the self-supporting insulated exhaust pipe of the present invention, it may be formed by any other desired method. For example, if the method can properly be controlled, the insulated tube can be formed by winding a layer of insulation 208 around the inner tube 204, then forming the outer tube 206 around the insulation s&hile the inner tube and the insulation are in place on the forming mandrel, or by forming the tubes 204 and 206 separately and then pushing the insulation into the annulus between the tubes while holding the tubes in their nal spaced positions. Whatever production method is used,' the final insulated tube will comprise concentrically arranged corrugated tubes having insulation ^extending between them along the length of the tubes. Note that it is not necessary in this embodiment to include longitudinal strips of higher density insulation* since this embodiment is not designed to be self-supporting and would not be subjected to as severe vibrations as in a self-supporting exhaust pipe.

Although this embodiment of the invention does not depend on the use "of any particular insulation, in practice the insulation, as in the first embodiment, must be sufficiently resistant to the high temperatures of exhaust**gases. Again, refractory fiber insulation is the most practical choice of insulation from the standpoint of resistance to temperatures exceeding 1600°F, and from the standpoints of insulating ability, cost and weight. Further, it^ low density of 4 pcf to 16 pcf permits the refractory fiber insulation to be wrapped around the inner corrugated tube without damage.

Although the dimensions of the corrugated strip may vary, it will be appreciated that the width of the strip will be fairly narrow in order to form tubes which will be only slightly larger in diameter than the outside diameter of the exhaust pipe over which it is to fit. In a typical arrangement, the inner and outer tubes may be formed of corrugated strips which are about 1 1/4 inches in width and which contain a number of corrugations, perhaps 5 to 7, in addition to the end flanges.

The material of the corrugated strips must be able to withstand the heat generated by the exhaust gases, be thin enough to enable maximum flexing of the corrugations when the tubes formed from the strip are pushed over bends in an exhaust pipe, and be able to withstand the stresses caused by the application procedure and the fatigue encountered during use. It should also be non- corrosive. The preferred material is stainless steel having a thickness in the range of 0.002 inch to 0.004 inch. This is considerably thinner than the metal of a corrugated tube intended to function as a self-supporting exhaust pipe, and is not strong enough to resist fatigue. Such extremely thin material, however, gives the corrugated tubes the flexibility needed to be moved over curved or angled portions of an exhaust pipe. If material thinner than about 0.002 inch were used the resulting tube would not have the necessary structural integrity, while material thicker than 0.004 inch would not have the necessary flexibility.

In use, a length of the insulated tube of this embodiment of the invention is pushed onto an exhaust pipe and moved along the entire extent of the pipe, at least up to the point at which a flange or other type of pipe mounting means is intended to be located. When the tube encounters a bend or curve in the exhaust pipe, the extreme flexibilty of the insulated tube enables it to conform to the curvature of the pipe. Thus in FIG. 24 the tube 200 has been trained over the curved portion of exhaust pipe 202, with the corrugations 210 being more widely spaced apart at the convex side of the curve and more closely spaced apart at the concave side of the curve than their original spacing.

In order to prevent moisture from entering the insulation at the ends of the tube it is preferred to provide an end enclosure. One way of accomplishing this is illustrated in FIG. 25, wherein the inner tube 204 extends beyond the end of the insulation layer 208 and the end of the outer tube 206, and is folded or flared back to the outer tube to form a circumferential lip 212. This arrangement not only encloses the end of the insulation 208, but also facilitates movement of the insulated "tube over the surface of the exhaust pipe by preventing- the possible snagging of the leading edge of the inner tube 204 on the exhaust pipe. Of course the same configuration can be provided at the other end of the tube in order to enclose the insulation at that end as well, even though snagging against the exhaust pipe is not a problem at the trailing edge of the tube.

Another way of enclosing the insulation and facilitating movement of the insulated tube over the exhaust pipe is illustrated in FIG. 26, wherein an end cap 214 has been provided between the inner and outer tubes. The end cap may be installed in any convenient manner, a preferred method being to melt a ring formed of zinc while held in place on the end of the insulated tube. The melted metal will bond to the tubes 204 and 206 to form a permanent enclosure.

The insulated tube may be held in place on the exhaust pipe by tack welding it directly to the pipe as illustrated in FIG. 25 at 216. In many cases, however, it will be unnecessary to provide any special attachment means. When installed on exhaust pipes that are sharply angled or curved, the gripping contact between the corrugations of the inner tube and the exhaust pipe in the angled or curved section will be enough to securely hold the tube in place.

As mentioned above, the range of wall thickness of the inner and outer metal tubes is 0.002 inch to 0.004 inch. Tubes intended to be trained over severely curved or angled exhaust pipe sections preferably are formed from the thinner metal, as the thinner metal facilitates the necessary bending. The inside diameter of the inner tube will also vary according to the outside diameter of the exhaust pipe and the severity of the bends in the exhaust pipe. A tube to be installed on a straight exhaust pipe, for example, could be of smaller inside diameter than a tube to be installed on a curved pipe. Although this dimension will necessarily vary according to conditions, for a curved exhaust pipe having an outside diameter of two inches, the inside diameter of the inner metal tube may be 2 1/4 inches and the inside diameter of the outer metal tube may be 2 3/4 inches, leaving room for insulation of 1/4 inch thickness.

It will now be appreciated that this embodiment of the invention provides an economical, simple, yet highly efficient means for insulating any or all of the various sections of exhaust pipe in an automotive exhaust system, thus functioning as a heat shield, conserving exhaust gas energy for quicker catalytic light-off and absorbing exhaust system noise.

In order to decouple an exhaust system from the engine manifold so as not to transmit torque from the engine to the exhaust system, the coupling of FIGS. 27-36 has been developed. Referring to FIG. 27, the upstream portion of an automotive exhaust system 220 is schematically illustrated as comprising an engine 222 and an engine exhaust manifold 224 connected to exhaust pipe 226 by the coupling 228 of this embodiment of the invention.

As shown in FIG. 28, the coupling 228 comprises an outer flexible tube 230 connected to end caps 232 and 234. The upstream end cap 232 is connected to an inlet tube 236 while the downstream end cap 234 is connected to an outlet tube 238. The direction of flow of exhaust gases from the engine manifold is indicated by flow arrows 240. Although the inlet and outlet tubes may be connected to the exhaust system in any effective manner, for purposes of illustration the inlet tube 236 is shown as being connected to the engine manifold 224 by means of mounting flanges 242 and bolts 244, and the outlet tube 238 is shown as' being connected to the exhaust pipe 226 by means 5f Λounting flanges 246 and bolts 248. The coupling is shown in the flexed condition caused by torque forces generated during engine acceleration and deceleration.

Referring to FIGS. 29 and 30, it can be seen that the inlet tube 236 comprises a downstream portion 250 of relatively small diameter and an upstream portion 252 of relatively large diameter. Similarly, the outlet tube 238 comprises a relatively small diameter downstream portion 254 of the same diameter as the inlet tube portion 250 and a relatively large diameter upstream portion 256 of* the same diameter as the inlet tube portion 252. In practice, the inlet and outlet tubes preferably would be formed from lengths of exhaust pipe which have been enlarged at one end to form the shape illustrated. The enlarged portion may be formed by any suitable means, such as by swaging or by welding a larger diameter tube to a standard exhaust pipe section. However formed, the larger diameter portions should be upstream of the sώaller diameter portions rather than in the reverse positions to prevent problems with back pressure and eddy currents in the exhaust gas flow.

The large"4 diameter portion 256 of the outlet tube 238 overlaps the small diameter portion 250 of the inlet tube 236 Qver a substantial portion of their lengths. The inside diameter of the enlarged portion 256 is greater than the outside diameter of the smaller portion 250 by an amount which provides for an annular space 258 between the portions 250 and 256 for a reason to be explained later. A flexible metal tube or hose 260 surrounds the inlet and outlet tubes 236 and 238 and is connected to them by suitable means to secure the flexible tube and the inlet and outlet tubes together as a unit. As illustrated in FIG. 29, a continuous weld 262 extending around the circumference of the inlet tube 236 connects the inlet tube to the upstream end of the flexible tube 260, while a continuous weld 264 extending around the circumference of the outlet tube 238 connects the outlet tube to the downstream end of the flexible tube. Because the flexible tube 260 should be radially spaced from the large diameter portion 256 of the outlet tube 238 situated between the extremities of the flexible tube, the welds 262 and 264 preferably engage the large diameter portions 252 and 256.

The outer flexible metal tube or hose 230 surrounds and is radially spaced from the first flexible tube 260 so as to provide an annular space for receiving a layer of insulation 266. As in the other previously described embodiments of the invention, the insulation may be of any type that will provide adequate insulating properties for the coupling, that is, being able to withstand exhaust gas temperatures in the range of 1600 "F to 1800°F. As before, the preferred insulation is refractory fiber insulation due to its of insulating ability, cost and weight. Further, its low density of 4 pcf to 16 pcf permits it to be wrapped around the inner flexible metal tube without damage and to compress as may be necessary during transmission of torque.

The outer flexible tube 230 is attached to the cylindrical legs 268 and 270 of the end caps 232 and 234 by continuous welds 272 and 274, which provide a seal to the insulation 266. The shoulder portions 276 and 278 of the caps 232 and 234 are attached to the inlet and outlet tubes by spot welds 280 and 282. This arrangement is shown also in FIG. 31, which is an end view of the downstream end of the coupling and shows the spaced spot welds 282. It will be understood that the spot welds 280 at the upstream end would be similarly arranged. The use of spot βlds at these locations instead of continuous welds Unfits heat transfer by conduction and also provides a path for the escape of water vapor which may have condensed within the confines of the spaced flexible tubes. By maintaining tight tolerances between the end caps"and tfie nlet and outlet tubes, moisture in the form of road splash will be prevented from gaining access to the insulation.

The frlexj-ble tubes 260 and 230 may be of any suitable construction which permits flexing. Preferably, since the flexible tubes are formed of metal in order to resist the temperatures to which they are exposed and to provide adequate strength, they are of corrugated construction, as shown in FIG. 29. As discussed in connection with other embodiments, and as shown in FIG.

32, the edges of the strip 284 used to form the flexible tubes are bent in upon themselves at 286 and 288 to form recesses or pockets in which similar shaped edges of adjacent, strips fit. The resulting tube is able to bend or flex without destroying its gas-tight construction. Although flexible metal tubes of this same general configuration are readily available, it will be understood,that other tube designs capable of providing a similar function may be employed if desired.

When the coupling of FIG. 29 is subjected to stresses tending to flex or bend it, the flexible tubes 230 and 260 will flex accordingly as illustrated in FIG.

33. The arrangement of FIG. 29, whereby the large diameter portion 256 of the outlet tube is spaced from both the inner flexible tube 260 and the overlapped small diameter portion 250 of the inlet tube, allows the flexible tubes to bend even though the inner flexible tube 260 is connected to the rigid inlet and outlet tubes. Thus as shown in FIG. 33, enough space has been provided forthe outlet tube 238 to become angled with respect to he inlet tube 236. Note that the lengths of the overlapping portions 250 and 256 are sufficient to provide a barrier to the flexible tubes against direct impingement of exhaust gases. Without this barrier the flexible tubes would not be able to withstand the hostile exhaust gas environment and would ultimately fail. During such flexing movement of the coupling, the insulation between the flexible tubes will be compressed to a degree at the inside radius of the bend and will be subjected to tension at the outside radius of the bend. The preferred insulation, being fibrous, is quite capable of accommodating this type of movement.

The arrangement of FIG. 29 is suitable for relatively short couplings which provide enough space for the overlapping inlet and outlet tubes to have sufficient relative angular movement. If, however, the flex requirements of the coupling are severe or the coupling cannot accommodate long overlapping lengths of tubing, the arrangement of FIG. 34 is preferred. In this modification the basic elements are the same and bear the same reference numerals as in FIG. 29, but an intermediate tube 290 has been added between the inlet and outlet tubes. The intermediate tube 290 is comprised of a relatively small diameter portion 292 and a relatively large diameter portion 294 of the same diameters as those of the inlet and outlet tubes. The large diameter portion 256 of the outlet tube overlaps the small diameter portion 292 of the intermediate tube, while the large diameter portion 294 of the intermediate tube overlaps the small diameter portion 250 of the inlet tube. By maintaining an annular space between the overlapping portions of the intermediate tube and the inlet and outlet tubes, and between the intermediate tube and the inner flexible tube in the same manner as in the first embodiment, and further by making the overlapping portions of the tubes sufficiently long, the inlet, outlet and intermediate tubes are able to angularly move relative to each other upon flexing of the coupling. This is further illustrated in FIG. 35, wherein the floating arrangement of the intermediate tube within the coupling which enables such angular movement is illustrated.

It is possible to lengthen the coupling or maximize the flexing even more by providing additional intermediate tubes. The arrangement of FIG. 36 illustrates such a modification wherein two intermediate tubes 296 and 298 are positioned between the inlet and outlet tubes 23-6 and 238. Both intermediate tubes have a floating arrangement whereby they are not connected to any of the elements in the coupling other than by being in overlapping engagement with each other and with the inlet -and* outlet tubes. The overlapped tubes will angularly move somewhat in the fashion of vertebrae to permit the flexible tubes to flex in response to stresses induced by-engine torque.

It will be appreciated that there are no set dimensions that must be adhered to since the individual requirements of specific installations will cause them to vary. The diameters of the tubes and the clearance between overlapped portions must be sufficient, however, to permit the necessary flexure while maintaining the overlapped portions of a length sufficient to prevent direct impingement of exhaust gases on the inner flexible tube. The flexure requirements will vary between types of vehicle^. The maximum flex angle requirement found to date has been in the order of 14° .

It is preferred that the inlet, outlet and intermediate tubes be formed from ordinary exhaust pipe tubing. By way of example, the small diameter portions of the tubes utilized in one embodiment were 2 inches in outside diameter and the large diameter portions were 2 1/16 inches in inside diameter, leaving a gap of 1/32 inch between the overlapped portions. In addition, the large diameter portions were spaced from the inner flexible tube by about 1/8 inch, and the length of the overlapped portions of the tubes was about 5/8 inch. t will now be appreciated that the coupling of this embodiment- of the invention provides an economical means of decoupling an automotive exhaust system from the engine manifold in terms of the transmission of stresses and vibration from engine torque. In addition, the decoupler of the invention also allows for expansion and compression of the exhaust system, thereby decoupling the engine on a three dimensional axis. Further, because of its unique design, the decoupler also isolates engine vibrations from the exhaust system, acting as a noise and vibration dampener.

The coupling is simple in construction, with the inlet and outlet tubes being held together by their connection to the inner flexible tube. The continuous weld employed for this conneciton makes the coupling gas- tight, preventing the escape of exhaust gases. The coupling also lends itself to being insulated by enabling the inner flexible tube to be surrounded with insulation.

It will now be apparent that the invention is not necessarily limited to all the specific features described in connection with the preferred embodiments, but that changes to certain features of the embodiments which do not alter the overall function and concept of the invention may be made without departing from the spirit and scope of the invention, as defined in the appended claims.

Claims

36 WHAT IS CLAIMED IS :
1. Ah insulated pipe for use in the exhaust system of a vehicle powered by an internal combustion engine , comprising: an inner metallic tube; an outer metal lic tube spaced from and concentrically arranged with respect to the inner metallic* tube; refractory fiber insulation f illing the space between the inner and outer tubes; a naj-όr portion of the insulation compris ing relatively! low density refractory fiber insulation; and a minor portion of the insulation comprising relatively. high density refractory fiber strips extending along the length of the pipe , the strips be ing circumferentially spaced from each other; the high density strips inhibiting movement of the low density fiber and preventing degradation thereof during operation of the vehicle.
2 . The insulated pipe of claim 1 , wherein the relatively" low density refractory fiber has a density in the approximate range of 4 pcf to 16 pcf and the relatively high density refractory fiber has a density in the approximate range of 24 pcf to 28 pcf .
3 . The insulated pipe of claim 1 , wherein the refractory fiber strips have a thickness greater than half the radial distance between the inner and outer tubes . .
4. A method for forming an insulated pipe for use in the exhaust system of a vehicle powered by an internal combustion engine , comprising the steps of : adhering a layer of refractory fiber insulation to the periphery of a f irst tube of relatively small diameter; and inserting the insulated first tube into a spirally corrugated second tube of relatively large diameter so that the layer of insulation contacts the second tube; the ^tep of inserting the insulated first tube into the second tube including the step of causing relative rotation between the second tube during relative reciprocal movement therebetween, the speed of the relative rotation being coordinated to the speed of the relative reciprocal movement to cause the insulated first tube to be threaded into the corrugations of the second tube.
5. In the exhaust system of a vehicle powered by an internal combustion engine, wherein the exhaust system includes an insulated pipe comprising an inner corrugated metallic tube and an outer metallic tube, the outer metallic tube being spaced from and concentrically arranged with respect to the inner metallic tube, and refractory fiber insulation filling the space between the inner and outer tubes, the improvement comprising: pipe attachment means including a conduit having two ends, one end of which is attached to an element in the exhaust system and the other end of which extends into the inner metallic tube of the insulated pipe at one end thereof; means on the conduit extending transversely therefrom and engaging at least one corrugation of the inner metallic tube to assist in holding the insulated pipe in place on the conduit; the inner corrugated tube being formed of spirally wound corrugated strip, and the transversely extending means being aligned at an angle to the conduit corresponding to the angle of the spirally disposed corrugations in the inside diameter of the inner tube, whereby the engagement of the transversely extending means with the corrugations permits the conduit to be threaded into the insulated pipe; a cap having a sleeve portion concentrically arranged with and spaced from the conduit and an end portion connected to the sleeve poration, the end portion being slidably mounted on the conduit, said one end of the insulated pipe extending into the space between the conduit and the sleeve portion of the cap and abutting the end portion of the cap; and the conduit further including stop means thereon, whereby threading of the conduit into the pipe causes relative movement between the insulated pipe and the conduit, the insulated pipe causing the cap to slidably move on h conduit until the cap engages the stop means.
6. In the exhaust system of a vehicle powered by an internal combustion engine, an insulated tube surrounding at least a portion of an exhaust pipe, comprising: an inner metallic tube having a slightly greater diameter than that of the exhaust pipe;
^ n outer metallic tube of greater diameter than that of the inner metallic tube, the outer tube being radially spaced from the inner metallic tube to form an annulus therebetween; -and* insulation filling the annulus between the inner and outer tubes, the insulation being capable of withstanding the tempeifature of exhaust gases in the exhaust pipe; the inner and outer tubes comprised of corrugations having a wall thickness in the approximate range of 0.002 inch to 0.004 inch, the corrugations making the inner and outer tubes sufficiently flexible so as to allow the insulated tube to be trained over nonlinear portions of the exhaust pipe.
7. The insulated tube of claim 6, including means enclosing the insulation adjacent the ends of the insulated tube, the insulated tube being at least partially held in place on the exhaust pipe due to contact between the corrugations of the inner tube and nonlinear portions*of the exhaust pipe.
8. In an automotive exhaust system having an engine manifold .and an exhaust pipe, a flexible coupling connecting the manifold and the exhaust pipe, comprising: a first flexible metal tube having upstream and downstream ends; a layer of insulation surrounding the first flexible metal tube; a second flexible metal tube radially spaced from the first flexible metal tube and surrounding the layer of insulation; an inlet tube extending through the upstream end of the first flexible metal tube, the inlet tube having an interior end located within the first flexible metal tube; an outlet tube extending through the downstream end of the first flexible metal tube, the outlet tube having an interior end located within the first flexible metal tube; the inlet and outlet tubes comprising portions of an exhaust gas flow path through the coupling; means for connecting the upstream end of the first flexible metal tube to the inlet tube and means for connecting the downstream end of the first flexible metal tube to the outlet tube; the interior ends of the inlet and outlet tubes being capable of substantial angular movement relative to each other upon bending of the first and second flexible metal tubes; and means for maintaining the second flexible tube in spaced relationship with respect to the first flexible tube.
9. The flexible coupling of claim 8, wherein each of the inlet and outlet tubes is comprised of a relatively large diameter portion upstream from a relatively small diameter portion thereof, at least substantial lengths of the relatively small diameter portion of the inlet tube and the relatively large diameter portion of the outlet tube being situated within the portion of the coupling surrounded by the first flexible tube, a substantial length of the relatively large diameter portion of the outlet tube overlapping a substantial length of the relatively small diameter portion of the inlet tube, the relatively large diameter portion of the outlet tube being spaced from the first flexible tube.
10. The flexible coupling of claim 9, including one or more additional tubes in the flexible coupling, each additional tube having a relatively large diameter portion upstream from a relatively small diameter portion, a substantial length of the relatively large diameter portion of the additional tube located farthest upstream overlapping a substantial length of the relatively small diameter portion of the inlet tube and being spaced from the first flexible tube, a substantial length of -the relatively large diameter portion of the outlet tube overlapping a substantial length of the relatively small diameter portion of the additional tube located farthest downstream, substantial lengths of the relatively large and small diameter portions of adjacent additional tubes overlapping each other, the additional one or more tubes being capable of angular movement relative to the. nlet and outlet tubes upon bending of the flexible metal tubes.
PCT/US1990/004253 1989-07-31 1990-07-30 Insulated exhaust pipe and method and means for producing and connecting same WO1991002143A1 (en)

Priority Applications (4)

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US386,841 1989-07-31
US07/386,754 US5004018A (en) 1989-07-31 1989-07-31 Insulated exhaust pipe and manufacture thereof
US07/386,841 US4998597A (en) 1989-07-31 1989-07-31 Insulated exhaust pipe attachment means
US386,754 1989-07-31

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EP0561019A1 (en) * 1992-03-18 1993-09-22 Firma J. Eberspächer Arrangement for positioning an inner shell in the casing of an exhaust device for vehicles
FR2697613A1 (en) * 1992-11-03 1994-05-06 Lhotellier Montrichard Sa Gas floe duct - made from two concentric layers of woven organic mineral material with space between filled with sound-absorbing substance
WO1995029327A1 (en) * 1994-04-27 1995-11-02 Aerospatiale Societe Nationnale Industrielle Exhaust pipe for a catalytic exhaust device
WO2001061164A1 (en) * 2000-02-18 2001-08-23 Friedmund Nagel Sound absorbing line
US6854925B2 (en) * 2002-09-03 2005-02-15 Ditullio Robert J. Storm water reservoir with low drag
CN102279106A (en) * 2011-03-31 2011-12-14 重庆长安汽车股份有限公司 Thermal insulation of the exhaust pipe means for detecting an engine for noise
US9512772B2 (en) 2013-09-16 2016-12-06 KATCON USA, Inc. Flexible conduit assembly
ES2713274A1 (en) * 2017-11-17 2019-05-20 Idr S L Cover for a rotary board of a thermal conduction

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US4351365A (en) * 1978-08-24 1982-09-28 Kabel-Und Metallwerke Gutehoffnungshutte Aktiengesellschaft Thermally insulated tube
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Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0561019A1 (en) * 1992-03-18 1993-09-22 Firma J. Eberspächer Arrangement for positioning an inner shell in the casing of an exhaust device for vehicles
FR2697613A1 (en) * 1992-11-03 1994-05-06 Lhotellier Montrichard Sa Gas floe duct - made from two concentric layers of woven organic mineral material with space between filled with sound-absorbing substance
WO1995029327A1 (en) * 1994-04-27 1995-11-02 Aerospatiale Societe Nationnale Industrielle Exhaust pipe for a catalytic exhaust device
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US6854925B2 (en) * 2002-09-03 2005-02-15 Ditullio Robert J. Storm water reservoir with low drag
CN102279106A (en) * 2011-03-31 2011-12-14 重庆长安汽车股份有限公司 Thermal insulation of the exhaust pipe means for detecting an engine for noise
US9512772B2 (en) 2013-09-16 2016-12-06 KATCON USA, Inc. Flexible conduit assembly
ES2713274A1 (en) * 2017-11-17 2019-05-20 Idr S L Cover for a rotary board of a thermal conduction

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