US3134457A

US3134457A - Engine exhaust muffler

Info

Publication number: US3134457A
Application number: US53526A
Authority: US
Inventors: Manley C Marcellus
Original assignee: Minnesota Mining and Manufacturing Co
Current assignee: 3M Co
Priority date: 1960-09-01
Filing date: 1960-09-01
Publication date: 1964-05-26
Anticipated expiration: 1981-05-26

Description

y 6, 1964 M. c. MARCELLUS ENGINE EXHAUST MUFFLER 2 Sheets-Sheet 1 Filed Sept. 1, 1960 FIG. 4

FIG.

INVENTOR.

MANLEY c. MARCELLUS ATTORNEY FIG. 2

May '26, 1964 M. c. 'MARCELLUS 3, 57

ENGINE EXHAUST MUFFLER Filed Sept. 1, 1960 2 Sheets-Sheet 2 FIG. 8 FIG.9

MANLEY C. MARCELL'US ATTORNEY INV EN TOR.

United States Patent I 3,134,457 ENGINE EXHAUST MUFFLER Manley C. Marcellus, East Oakdale Township, Washington County, Minn, assignor to Minnesota Mining and Manufacturing Company, St. Faul, Minm, a corporation of Delaware Filed Sept. 1, 1960, Ser. No. 53,526

4 Claims. (Cl. 181-56) This invention relates to articles for treatment of the exhaust gases of internal combustion engines and particularly to devices for mufiling the noise of automobile engmes.

The art is replete with devices proposed for the mufiling of automobile engines and particularly with devices incorporating metallic baffle plates in various arrays. However, the presence of metallic baffles (and by this term it is meant include any metallic arrangement for absorption of or deadening sound), is constantly beset by a severe problem in corrosion resulting from exposure to water vapor and corrosive fumes at certain temperatures. Commonly such corrosion effects the baflies and internal construction of mufilers as well as the external parts of these devices, for examples, the housings or casings, because the latter remain cooler. It is, of course, possible to overcome this corrosion, but at uneconomic price, by use of noble metals or at least theoretically noncorrodible base metals. Such expedients as the use of metal of relatively great thickness or of ceramic-coated metal are of course still subject to disadvantages of cost, and may increase the size and weight of the muffier.

It is an object of this invention to provide an acoustical mufliing device for internal combustion engines which is much less subject to corrosion.

A further object of the invention is to provide an effective light-weight mufiier for automobiles.

Another object of the invention is to provide an exhaust noise muffler for internal combustion engines which is simple in construction and easily assembled. Other objects will become evident hereinafter.

It has now been found that an effective auto exhaust mutfler is produced by positioning a packing consisting essentially of numerous ordered passages of relatively great lengthzwidth ratio formed from certain mineral or inorganic materials in sheet form, and preferably from mica sheets, in a casing having inlet and outlet means and a centrally disposed packing chamber. The packing employed has a plurality of ordered passageways, preferably straight parallel passages, formed by the said corrugations in adjacent layers, and these passageways have a lengthdiameter ratio ranging from about 10:1 to about 80:1. The said passageways are at least of greater cross-sectional height than the thickness of the sheets which are used, and

are so disposed in the chamber as to produce effective cross-flow of the exhaust gases between the inlet and outlet plenums of the device.

The mufilers of the invention and their operation will be more clearly understood from the following description.

. Referring to the drawings:

FIGURE 1 is a view in perspective, partially broken away to show details, of a lightweight mufller of the invvention having a generally rectangular box-like configuration.

FIGURE 2 is a cross-sectional view of the muffier of FIGURE 1, taken along line A- -A'.

FIGURE 3 is a view in perspective of a retainer for helically wound sound absorbing units.

FIGURE 4 shows an exhaust gas manifold adapted for use with the retainer shown in FIGURE 3.

FIGURE 5 is a view, in perspective and in transverse cross-section through the midpoint of the longitudinal axis of a complete mufiier emploiyng the retainer shown in FIGURE 3 and manifolds shown in FIGURE 4.

FIGURE 6 is an exploded view in perspective of an embodiment of the invention employing rectangular mutiling units and manifolds for exhaust gases for use therewith.

FIGURE 7 is a view in perspective and transverse crosssection through the midpoint of the longitudinal axis a complete mufiler employing the elements shown in FIG- URE'6.

FIGURE 8 is a view in perspective and greatly enlarged of a portion of a mufiling unit composed of alternating flat and corrugated sheets.

FIGURE 9 is an end view, greatly enlarged, of a helically wound mufiiing unit.

Referring to the drawings, in FIGURE 1 a generally rectangular box-like casing 12 is provided with a gas inlet 13 at one end corner, and a gas outlet 14 at the diagonally opposite end corner. The top 16 and bottom 17 are conveniently made removable and are fastened to the sides by bolts or the like, although the whole unit may be welded together if desired. A portion of the casing is broken away to show the interior construction. The inlet 13 provides access to the plenum space or manifold 18 defined by the sides and ends of the casing and the face of the mufiiing assembly designated generally as 20. The mutiling assembly 20 consists of a number of helically wound corrugated muflling units 21, and a retaining frame 22 adapted to contain the mufiling units between the sides thereof and provided with openings so that the gases may flow through the muffling units. A refractory, fibrous or nonfibrous packing (not shown) may be used to fill spaces in the assembly through which exhaust gases might bypass the mufiiing units. Alternatively the muifiing units are inserted in metal cylinders which are aligned with the openings in the retaining frame and are welded in place. The cross-sectional view shown in FIG. 2, taken along line AA of FIG. 1, also shows the arrangement of the device in which body 12 having

cover plates

16 and 17 encloses retaining frame 22 in which is positioned rnufiling unit 21. In operation, exhaust gases enter the inlet plenum 18, pass in cross-flow through the muffiing unit 21 and out through exhaust plenum 19 and outlet 14. It will be noted that the muffling units are not shown to scale as respects the corrugations, which are here much exaggerated to show the helical and corrugated structure and the finite thickness of the corrugated and flat sheets of which the unit is composed. Referring to FIG. 8, there is shown a portion of a mufiling unit 24 composed of alternate corrugated sheets 25 and fiat sheets 26. The sheets need not be adhered to each other, but such a blockshaped unit is more conveniently handled when adhered so as to be substantially unitary. In FIG. 9 there is shown another form of muflling unit 21 in which corrugated sheet 28 and flat sheet 29 are superimposed and then rolled up together into a roll of desired diameter.

In FIGURE 3 there is shown a casing 28 (conveniently made by joining two identical half-sections of the configuration shown) adapted to contain a number of mufiiing units 21 for use in another embodiment of the invention.

FIGURE 4 shows a manifold 31, having gas outlet 31, and provided with openings 32 adapted to fit on the ends of the casing 28 of FIG. 2, to provide a passage for conducting gases to or from the muffling units 21. In FIG- URE there is shown, in transverse cross-section on a line which bisects one of the muflling units 21, a completed embodiment of the invention. The device has an over-all elliptical cross-sectional aspect and consists of a cover 34 composed of

halves

35 and 36 joined at their edges. -While not shown in the drawing, the cover ex-' tends over the ends of the unit so as to enclose and retain in position manifolds 30 (shown in FIG. 4) fitted in place over the endsof the cylindrical portions of casing 28 (FIG. 3). All of the generally cylindrical passages in casing 28 are filled with helically coiled muflling units 21. The upper and lower halves of the cover 34 may be separably fastened to provide for the insertion of new muffling units when one or more requires replacement. The ends of the casing 28 which are adapted to fit into the holes 32 in the face of the manifold 30 shown in FIGURE 4 may be provided with gaskets if desired, al-' though this is not required. Joining can be effected by welding, but preferably bolts are used so that the outer casing is removable for replacement of the muffling units. With this type'of construction, the manifolds, retaining means and casings can be made of corrosion-proof metals and the silencing means (which is then the only portion of the muffler which may deteriorate, and then owing only to possible clogging with particulate matter) can be replaced easily. It is not necessary to remove the connections to the exhaust pipe or tail pipe of the automobile, which removal is ordinarily very time-consuming. .It will be evident that the two manifolding units can be combined with the mufller assembly with the tubular part connections at the opposite ends for con ventional arrangements, or at the same end if desired. In operation, the exhaust gases enter through an inlet pipe and manifold, pass in cross-flow through the mufiling unit, and exit through a manifold and exhaust pipe. Since the unit as shown in FIG. 5 is symmetrical, it is immaterial which manifold 30 is used as the inlet manifold. FIGURE 6 shows an exploded view, without an outer casing, of another embodiment of the invention. The same embodiment is shown assembled with an outer casing in partial cross-section in FIG. 6. In thisembodiment the silencing is effected by muflling units 24 made up ofalternate corrugated sheets 25 and plane sheets 26 (shown in enlarged detail in FIGURE 8), laid up into a block. The flat muffling unit may be of such dimensions that several, e.g. two, four or more are required to fill the retaining frame 40, or one large unit may be employed. The structure illustrated in FIGURE 6 is shown to consist of not more than four such muffling units, but greater numbers can easily be provided if desired. The retaining frame 40 is made from a suitable sheet metal cut to provide openings 41 in both sides (here shown only at the front), separated by vertical struts 42, which alternatively may be fiat plates extending across the entire Width of the frame, thus serving to baflle the spaces between mufiling'units when more than one are used. The retaining frame has end plates 44 and reinforcing bars 45. Depending upon preference in manufacturing procedures, the retaining frame may be fabricated as a unit which is die-cut and bent to form, or a group of smaller parts maybe assembled. The

manifolding units

46 and 47 are identical and consist of a body portion of generally arcuate cross-section and hollow as shown, the open side of which is adapted to fit against and seal the edges of frame 44 on the sides which are open.

Tubes

49 and 50 serve as inlet or exhaust outlets. Thus, the open faces of the manifolding units mate with the respective open faces of the mufiling assembly when assembled and are conveniently held in frictional engagement by an outer casing. Alternatively, of course, these parts can be bolted or welded together and an outer casing can be omitted.

FIGURE 7 shows in partially cross-sectional perspective View the elements shown in FIG. 6 assembled and covered with a casing 52. The plenums 53 through which the gases flow, which are formed by the manifold means 46 or 47 and the open faces of casing 40, are shown. The operationof the device is susbtantially the same as that of the mufflers shown in FIGURES 1 and 5.

The muflling units employed in the mufflers of this invention are conveniently prepared from mica sheets (thin, flexible sheets of material formed by producing a sheet from a pulp of mica particles). These can, for example, be made by laying up corrugated sheets of synthetic mica prepared from the synthetic tetrasilicic fluorine micas described by Robert A. Hatch, United States Patent No. 3,001,571, which can be represented by the general formula:

wherein Z represents a total of one atom of desired profor example, by casting a suspension of the finely divided mica on a screen such as in a Fourdrinier paper making machine, draining off the water in the usual manner and calendering the sheet thus formed.

Natural mica can also be split into very small platelets and used to form sheets. Thus, for example, sheets of mica of the character employed herein can be prepared according to known methods, e.g. as disclosed in United States Patents 2,791,262 and 2,842,183. Other inorganic V or mineral materials which can be fabricated into somewhat flexible corrugated sheets, and which are stable at the maximum temperatures ordinarily encountered in exhaust gas mufflers for internal combustion engines,

namely up to about 600 C. under load, can be used to" produce the mufrling units. Such sheets have properties which are suitable for use for the purposes of the invention, similarly to the mica sheets described. While temperatures of the order of about 600 C. encompass the range of maximum temperatures encountered in ordinary practice, it is obvious that materials stable above 600 C. can be used, i.e. those which retain their original character of sheet-form and flexibility without substan tial change. It is important that these materials do not irreversibly lose bound water at temperatures in the range specified with adverse results to their strength and flexibility, as, for example, in the case' of asbestos fibers, which dehydrate irreversibly to become powdery and lose strength at about 450 C.

In the preparation of the mufiler packing units employed in this invention some of the sheets employed are corrugated by passage between mating rollers which impress the sheets with a corrugated pattern of alternating grooves and ridges. vention the dimensions of the corrugations should be in the range of from about 3 to about 20 complete corrugations per inch. The depth of the grooves'may range from about 0.5 to about 1.5 times the width. Thus, when.

there are 5 corrugations per inch each groove will be 0.20 inch Wideand may be from 0.10 to 0.30 inch in depth, when there are 15 corrugations per inch each V groove will be .067 inch wide and may be from-0.033 to 0.10 inch deep.

The individual sheets which are used are of av thickness equal to about one third or less that of the depth of the grooves. Since the purpose of the sheets is to define the small ordered passageways, the sheets, need For the purposes of the in-' 5 be only thick enough to provide a self-supporting structure and it is generallydesirable that the thickness be the minimum necessary to provide this degree of strength. The thickness will consequently depend to some extent upon the characteristics of the mica used to make the sheets, and ranges from about 5 to 50 mils. The mica sheets prepared from very small mica flakes or particles possess a certain degree of flexibility which in the structures here described apparently serves to absorb even rather severe mechanical shock when distributed over the innumerable small segments of sheets defining the passageways. I v

The separate sheets comprising the packing may be laid up without binder but somewhat greater rigidity is obtained by employing a binder such as water glass or aluminum phosphate cement, so that the sheets serve to reinforce one another. This assists in distributing V mechanical stresses throughout the packing.

A number of arrangements of the sheets are possible. When the corrugations run directly across the sheet (at right angles tov the edges) it is generally desirable to alternate flat and corrugated sheets, adhering the ridges of the latter to the flat sheets. The assembly is then dried and can be trimmed or cut to the dimensions necessary for the desired packing configuration. If desired, although this is somewhat more difficult, directly superimposed corrugated sheets may be adhered together at the ridges to give generally more round .passageways as contrasted to the more or less triangular or semi-circular passageways when flat sheets are interpolated between successive corrugated sheets. If preferred the successive corrugated sheets may be positioned with the corrugations at an angle rather than parallel, usually not over about 45, and the ridges then adhered where they cross. Thus, it is possible to corrugate the sheets at an angle less than 90 relative to the long axis of the sheets and thus to produce packings with diagonal arrangement of the passageways. variations in which the passageways are diagonal at various angles to the long axis of the packing are thus possible. The fabrication of these sheets and adhering them is however only a part of this invention to the extent that packings adapted to produce elfective cross-flow are produced. In muflier packings of the invention utilizing helically wound units, as well as in that in which flat sheets are used, it is not necessary that all of the corrugated sheets have the same number of corrugations per inch and'the provision of passageways of different cross-sectional dimensions is desirable for acoustic purposes, or to provide for decreased resistance to gas flow at the outlet end of the device, or the like.

A convenient methtod for laying up a useful mufiler packing unit is to superimpose a long corrugated sheet on a long flat sheet and to wind them up into a roll, so that the passageways run between the two ends of the roll. It is not necessary that the two sheets be sufficient in length for the entire roll. Additional pieces can be introduced during rolling without materially affecting the value of the packing, and the sheets need not be adhered since slight compression of the cylindrical roll within the muffler holds the unit in shape.

Six units about 4 inches in diameter formed from approximately 4 wide sheets about 5 mils thick, the corrugated one having 15 corrugations per inch at right angles to the edge, are arranged in a frame and placed in a casing as shown in FIGURE 1. The spaces may be packed with glas fiber, or fibers of aluminum silicate (available under the trademark name Fiberfrax) if desired, but to avoid excessive bypass of exhaust and to retain the separate rolls in position it is only necessary to compress the units somewhat. This is readily done by providing rolls of such size that they are under slight pressure vertically and laterally after the cover plates are attached. When this muffler was attached to a 1959 model automobile having a 270 H.P. engine of 371 cu. in.

It will be evident that numerous displacement, it was found to impose back pressure on the exhaust gases equal to about 10 inches of water at 60 m.p.h. speed. The back pressure was much less at lower speeds. The car was test driven for 17,000 miles mainly at speeds of about 60 m.p.h. and the mufiler was then opened and the packing inspected. It was found that there had been slight plugging of some of the passageways by lead deposits from the gasoline but that the packing was otherwise sound. The muflling efIect of the packing was on the average (over the range of sound frequencies emanating from the exhaust stream) approximately that of the conventional mufller employed as a stock item on this car. The same muffler was replaced on the car and the use of the car was continued. The muffler was removed and inspected again after about 45,600 miles of driving. There was no appreciable deterioration of the unit. A slight deposition of particulate matter derived from the exhaust gases, such as particles of lead oxides, was observable on the inlet faces of some of the passages, but the unit was considered to be in satisfactory condition for prolonged further use.

What is claimed is:

1. In an automobile exhaust mufiler, in combination, a casing, inlet and outlet means connected with opposite sides of said casing, and means retaining gas-permeable packing in said casing for traverse by exhaust gases between said inlet and outlet means, said packing consisting essentially of multilayers of flexible corrugated and flat mica sheets which are stable at temperatures up to at least about 600 C. providing a plurality of ordered passageways of relatively large length-diameter ratio formed by the said corrugated and fiat mica sheets in adjacent layers, the said passageways being disposed so as to require effective cross-flow of the exhaust gases from said inlet means to said outlet means.

2. In an automobile exhaust mufller, in combination, an inlet manifold, an outlet manifold, packing-containing retaining casing having openings adapted to cooperate with the said manifolds for pasasge of exhaust gases from said inlet manifold to said outlet manifold, silencing packing disposed throughout the said retaining casing consisting essentially of multilayers of flexible corrugated and flat mica sheets having a plurality of ordered passageways of relatively great length-diameter ratio formed by the said corrugated and flat mica sheets in adjacent layers, said passageways being disposed so as to require effective cross-flow of exhaust gases from said inlet manifold to said outlet manifold through said packing, and an outer casing enclosing said inlet and outlet manifolds and said packing-containing retaining casing.

3. In an automobile exhaust mufller, in combination, a casing consisting of a packing chamber and inlet and outlet means for exhaust gases connected with said chamber, and packing disposed in said packing chamber and adapted to channel exhaust gases through said chamber consisting essentially of multi-layers of flexible corrugated and fiat mica sheets having a plurality of ordered passageways of length-diameter ratio greater than about 1021 formed by the said corrugated and flat mica sheets in adjacent layers, the said passageways being disposed so as to require effective cross-flow of exhaust gases from said inlet means to said outlet means.

4. In an automobile exhaust muffler, in combination, a box-like retaining casing having a top, bottom and ends and openings on each of two opposite sides thereof, silencing packing disposed throughout the said retaining casing consisting essentially of multilayers of flexible corrugated and flat mica sheets having a plurality of ordered passageways of relatively great length-diameter ratio formed by the said corrugated and flat mica sheets in adjacent layers, said passages connecting the openings on the sides of said retaining casing; manifolding means for inflow and outflow of exhaust gases attached to the sides of said retaining casing enclosingthe openings in the sides of said retaining casing; exhaust inlet and outlet means .References Cited in the file of this patent UNITED STATES PATENTS 1,209,315 Malley Dec. 19, 1916 1,366,147 Worthington Jan. 18, 1921 1,811,762 Schnell June 23,1931 1,887,305 Helmore et a1. Nov. 8, 1932 1,921,468 Jack Aug'. 8, 1933 Nelson Mar. 9, Blanchard Sept. 9, Heyman Dec. 23, Traynor Aug. 16, Friend Mar. 21, Thompson Apr. 11, Hatch Sept. 26,

FOREIGN PATENTS France 'Mar. 31, Switzerland Apr. 5, Austria Oct. 25,

France Nov. 3,

Claims

1. IN AN AUTOMOBILE EXHAUST MUFFLER, IN COMBINATION, A CASING, INLET AND OUTLET MEANS CONNECTED WITH OPPOSITE SIDES OF SAID CASING, AND MEANS RETAINING GAS-PERMEABLE PACKING IN SAID CASING FOR TRAVERSE BY EXHAUST GASES BETWEEN SAID INLET AND OUTLET MEANS, SAID PACKING CONSISTING ESSENTIALLY OF MULTILAYERS OF FLEXIBLE CORRUGATED AND FLAT MICA SHEETS WHICH ARE STABLE AT TEMPERATURE UP TO AT LEAST ABOUT 600*C. PROVIDING A PLURALITY OF ORDERED PASSAGEWAYS OF RELATIVELY LARGE LENGTH-DIAMETER RATIO FORMED BY THE SAID CORRUGATED AND FLAT MICA SHEETS IN ADJACENT LAYERS, THE SAID PASSAGEWAYS BEING DISPOSED SO AS TO REQUIRE EFFECTIVE CROSS-FLOW OF THE EXHAUST GASES FROM SAID INLET MEANS TO SAID OUTLET MEANS.