US 3908372 A
Description (OCR text may contain errors)
United States Patent [1 1 Fowler et al.
[ 1 Sept. 30, 1975 1 1 HEAT SHIELD FOR EXHAUST CONDUITS  Inventors: Charles P. Fowler, Jackson; Robert N. Balluff, Rives Junction, both of Mich.
 Assignee: Tenneco lnc., Racine, Wis.
 Filed: Aug. 15, 1974  Appl. No.: 497,672
 US. Cl. 60/320; 23/288 F; 138/114  Int. C1. ..F01N 3/14; F16L 11/00  Field of Search 60/298, 320, 272, 286, 60/299; 23/288 F; 138/131, 134, 38, 114;
 References Cited UNITED STATES PATENTS Cullom 138/114 Heath 60/320 Kern 60/320 Primary E.\'aminerDouglas Hart Attorney, Agent, or FirmHarness, Dickey & Pierce  ABSTRACT A flexible heat shield for the outside of a conduit of an internal combustion engine exhaust system comprises numerous metal coils, preferably parts of a helical strip, which longitudinally overlap on one edge and have standoff flanges engaging the conduit on the other edge, the coils being perforated in accordance with a program that locates the holes on the bottom side of the conduit.
1 Claim, 3 Drawing Figures U.S. Patent Sept. 30,1 975 3,908,372
HEAT SHIELD FOR EXHAUST CONDUITS BRIEF SUMMARY OF THE INVENTION It is the purpose of this invention to provide a heat shield for an exhaust system conduit that is imperforate on top, perforate on the bottom, and flexible.
The invention accomplishes this by means of a series of separate, relatively movable metal coils, preferably interconnected in a helical strip, that overlap each other and have flanges to space them from the conduit. The coils are preferably made from strip metal that is intermittently perforated in a numerically controlled punch press operation so that when the coil is slipped on a pipe, the holes will be on the bottom.
DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic side elevation of a motor vehicle internal combustion engine exhaust system having a conduit heat shield embodying the invention;
FIG. 2 is a cross section along the line 2-2 of FIG. 1; and
FIG. 3 is a cross section broken away, along the line 3-3 of FIG. 2.
DESCRIPTION OF THE INVENTION An internal combustion engine 1, of the type used on automobiles and trucks such as indicated by phantom line V, has an exhaust manifold 3 that discharges exhaust gas into an exhaust pipe 5 that is part of an exhaust system 7. The pipe 5 carries gas to a gas treating unit 9 such as an acoustic silencer (muffler) or an emission control device, e.g., a catalytic converter. A tailpipe 11 carries treated gas away from the unit 9 to discharge it through an open end 13 into the atmosphere.
The invention is of special use when the device 9 is a catalytic converter. In accordance with the invention a metal shield 15, preferably low carbon sheet steel strip, is disposed around at least those portions of the tailpipe that are likely to be dangerous because of their high temperature. The shield comprises numerous individual annular coils 17 that are preferably the separate but interconnected turns of a helically coiled strip of steel. Tailpipes normally contain one or more bends in them, as illustrated at 19 and by the gap 21, and the shield of this invention may be installed after the pipe is bent by slipping it over an end of the pipe and moving it longitudinally to the desired location.
The coils 17 each have a short transverse flange 2 along one edge that engages the outer surface of the conduit and serves to space the main longitudinally extending portion of each coil from the conduit. The other edge 27 of each coil rests on top of and overlaps the flanged edge of the adjacent coil, the length of the overlap being long enough to prevent actual separation of the coils on the outside of any bend in the conduit. Due to metal thickness, the portions 25 have a slight taper and this provides some elastic pressure between the overlapped portions of adjacent coils.
The space between each coil and the conduit comprises an air gap 29. In the form shown the gaps of each individual coil actually merge into each other to form one continuous, helical gap extending the full length of the shield and preferably open to atmosphere at each end. The bottom sides or halves of the gaps preferably open to atmosphere by way of several apertures 31 formed in the coil portion 25. The top sides or halves of the coils are preferably imperforate, however. This arrangement provides maximum shielding of the top of the hot conduit while permitting the flow of cooling air through the gaps and out of the apertures 31 in the bottom of the coils. Thus, the floor of an automobile, for example, is shielded from the top of the conduit and grass, weeds, etc., are shielded from actual contact with the bottom of the conduit.
As indicated above, the apertures 31 are prepunched in the strip from which the coils are formed in precontrolled patterns that cause them to be located on the bottom when the shield is slipped on the pipe. A numerical control program can be used to control the hole formation on a punch press; and it can be rather easily varied to accommodate variations in pipe shape, bends, etc., as compared with costs of retooling to change hole location. If desired the shield may be welded, bolted or otherwise secured to the conduit to positively prevent it from creeping out of position. Certain types of exhaust system hangers (not shown) may provide tight clamps that extend around the shield to prevent creeping.
Modifications may be made without departing from the spirit and scope of the invention.
1. In an internal combustion engine exhaust system including a gas treating device and a horizontally extending exhaust gas flow conduit having an outer surface and connected in series to the device, a heat shield mounted on the conduit and comprising a series of Iongitudinally overlapping annular coils that are longitudinally adjustable relative to each other whereby they may be fitted over bends in the conduit while substantially maintaining longitudinal contact with adjacent coils, each of said coils having a transverse flange along one edge that contacts the outer surface of the conduit to space the coil from said outer surface, the other edge of the coil slidably fitting on the outside of the flanged edge of the adjacent coil, the space between the coil and the outer surface of the conduit comprising an air gap, at least the top half of said coils being imperforate, the bottom half of said coils containing apertures to provide for the flow of air through the coil, said coils comprising interconnected turns of a helically coiled