US3378099A

US3378099A - Muffler and outlet tube for small internal combustion engines

Info

Publication number: US3378099A
Application number: US667914A
Authority: US
Inventors: Gordon Douglas
Original assignee: Briggs and Stratton Corp
Current assignee: Briggs and Stratton Corp
Priority date: 1967-09-15
Filing date: 1967-09-15
Publication date: 1968-04-16
Anticipated expiration: 1985-04-16

Description

April 16, 1968 D. GORDON 3,378,099

MUFFLER AND OUTLET TUBE FOR SMALL INTERNAL COMBUSTION ENGINES Filed Sept. 15, 1967 2 Sheets-Sheet l Snack/44%;

35 {Quakes Simian i 1%,,

April 16, 1968 D. GORDON 3,378,099

MUFFLER AND OUTLET TUBE FOR SMALL INTERNAL COMBUSTION ENGINES Filed Sept. 15, 1967 2 Sheets-Sheet 2 f I .3. i

SPOT WELDED SPOT WELDED United States Patent 01 fee 3 378 099 MUFFLER AND OUTLET TUBE FGR SMALL INTERNAL COMBUSTIQN ENGENES Douglas Gordon, Hartford, Wis, assignor to Briggs &

Stratton Corporation, Wauwatosa, Wis, a corporation of Delaware Filed Sept. 15, 1967, Ser. No. 667,914 11 Claims. (Cl. 181-40) ABSTRACT OF THE DISCLOSURE An outlet tube from which engine exhaust gas is discharged in a desired direction has a fiat elongated balfle plate in its downstream portion which cooperates with the tube to define two passages, one generally convergent downstream and the other generally divergent. The wall portion of the tube that defines the divergent passage has a large notch opening .to its discharge end. The downstream portion of the bafiie plate has lengthwise elongated apertures.

This invention relates to exhaust mufilers for internal combustion engines and refers more particularly to a muffling outlet tube that is especially adapted for use on single cylinder engines and by which exhaust gases issuing from the engine are caused to be discharged in a desired direction and to a desired zone or location near the body of the engine.

In many small engine installations, and particularly on small riding tractors and riding mowers, it is highly desirable to provide for discharge of engine exhaust gases in a desired direction or to some particular zone near the engine body, in order to avoid the possibility of having a concentrated stream of exhaust gases blown against a person standing near the engine or against delicate plants or the like near which the engine is moved. in many cases it is desirable that the exhaust gases be discharged in a direction generally opposite to that in which they leave the engine body. Thus, if an exhaust port is located at one side of an engine cylinder body, the desired outlet would direct the emergent gases generally back across or over the cylinder body or cylinder head.

-In most cases the provision of a plain outlet tube on the muffler of a small engine for effecting such controlled discharge of exhaust gases results in a substantial increase in exhaust noise so that the exhaust tube actually cancels some of the silencing effects of the muffler.

An example of the noise augmenting effect of a plain outlet tube is provided by experience with a muffler similar to that disclosed in Patent No. 3,168,936, issued Feb. 9, 1965 to Douglas Gordon. The mufller of that patent had an expansion chamber comprising a pair of relatively shallow and generally rectangular pan-like shell members, with 'bafiie means in its interior. It had an inlet port in its rear wall and had an outlet deflector at its front that was adjustable to cause exhaust gases to be discharged either parallel to the direction in which they flowed into the expansion chamber or in substantially any direction at right angles to the direction of entry. When used with its regular outlet, that muffler provided very satisfactory silencing.

However, an attempt was made to adapt that mufiier for so-called reverse flow, whereby the exhaust gases would be caused to undergo about a 180 change of direction in the course of flow through the mutiier.

To this end an outlet port was provided in the rear of the expansion chamber, instead of at its front, and a plain outlet tube was fastened to its rear, in register with the outlet port, to conduct exhaust gases partway back across the cylinder to a discharge zone alongside the cylinder 3,378,999 Patented Apr. 16, 1968 head. It was found that the muflier so modified was substantially more noisy than in its original form as disclosed in Patent No. 3,168,936, and that the outlet tube was responsible for the higher noise level.

With the foregoing comments in mind, it is a general object of this inventioin to provide a mufi'ler outlet tube for small single cylinder engines whereby engine exhaust gases can be discharged'in a desired direction and to a desired zone, which outlet tube does not increase the noise level of the mufiier.

Another object of this invention is to provide a mufiier generally similar to that of Patent No. 3,168,936, but from which exhaust gases are discharged in a direction generally opposite to that of their entry into the Inufiler and having an outlet tube from which exhaust gases can be discharged at a distance from the rnuflier body and which provides good muflling without absorbing an undue amount of engine power.

Another specific object of this invention is to provide an exhaust mufiier outlet tube of the character described that is readily adjustable to some extent to enable its discharge end portion to be set in any of a number of different positions that will accommodate various installation conditions and situations.

With these observations and objects in mind, the manner in which the invention achieves its purpose will be appreciated from the following description and the accompanying drawings. This disclosure is intended merely to exemplify the invention. The invention is not limited to the particular structure disclosed, and changes can be made therein which lie within the scope of the appended claims without departing from the invention.

The drawings illustrate one complete example of the physical embodiment of the invention constructed according to the best mode so far devised for the practical application of the principles thereof, and in which:

FIGURE 1 is a fragmentary perspective view of a portion of a single cylinder engine on which there is installed an exhaust rnufiler embodying the principles of this invention;

FIGURE 2 is a view in rear elevation of the muffler itself, with portions shown broken away;

FIGURE 3 is a sectional view taken on the plane of the line 3-3 in FIGURE 2; and

FIGURE 4 is a fragmentary sectional view through the outlet tube, taken on the plane of the line 44 in FIGURE 3.

Referring now more particularly to the accompanying drawings, the numeral 4 designates generally the cylinder portion of a single cylinder engine having an exhaust mutiler 5 fastened to one side thereof so that an inlet opening 6 in the rear of the rnufiier is in register with an exhaust port 7 in the side of the cylinder body. Exhaust gases entering the mufiier 5 from the exhaust port 7 undergo a substantially complete reversal of direction in the course of flow therethrough and are discharged to a zone generally near the cylinder head and about halfway across it from a rearwardly projecting outlet tube 8 on the mufiier that embodies the principles of this invention.

The mufiler comprises complementary front and rear pan-like shell members 10 and 11 that cooperate to define an expansion chamber 12. Within the expansion chamber are an inlet bafile 13 that also performs a structure supporting function described hereinafter, and a second baffle 14. There is also a baffle 15 in the outlet tube 8.

The front shell member 10 has a rim 16 around its edge that is clinched around a flange-like rim 17 on the rear shell member 11 to hold the shell members assembled. The expansion chamber, as viewed from the front or the rear thereof, is generally rectangular in outline, but has rounded corners. The inlet opening 6 is formed in the rear shell member, near one corner thereof, and is adapted to register with an exhaust port 7 in the side of an engine cylinder body. Near its opposite corner the rear shell member has an outlet opening 19 with which the outlet tube 8 registers.

The rear wall of the rear shell member comprises two

wall portions

20 and 21 that are obliquely inclined to one another at an obtuse angle. The wall portion 20' in which the inlet opening 6 is formed is generally perpendicular to the side walls of the expansion chamber and parallel to its front wall. The other wall portion 21, in which the outlet opening 1? is formed, slopes forwardly and toward the corner nearest the outlet opening.

The muffler can be secured to an engine body by means of bolts 22 extending through coaxially aligned holes in the front and rear walls of the expansion chamber and received in threaded holes in the cylinder. The inlet baffle 13, which extends edgewise between the front and rear walls of the expansion chamber, substantially parallel to the axis of the inlet opening, supports those walls against the converging forces that the bolts 22 exert upon them as the bolts are tightened, and a small plate 24 through which both bolts pass overlies the front wall to distribute those forces. If desired, a heat shield plate 25 can be interposed between the rear wall of the expansion chamber and the cylinder to afford protection to a fuel line 26 or other part that should not be subjected to high heat.

The inlet bafile 13 is generally similar to that of Patent No. 3,168,936, comprising a tube bent from a fiat blank to a general diamond shaped cross section but with rounded corners, and having numerous perforations. A portion of the rear wall of the expansion chamber around the inlet opening 6 is slightly dished, as at 27, to receive the rear end of the inlet baffle with a close nesting fit, for steadying the battle during assembly of the unit. The inlet bailie is further held against lateral shifting by the bolts 22, which extend along its remote inner corners.

The inlet bafiie is bent in such a way that its adjacent edges are slightly spaced apart, as at 28, and is so mounted that the said edges are nearest the adjacent corner of the expansion chamber. Its wall portions bounded by the edges just mentioned have substantially shallow notches 29 that open to said edges and to the front edge of the baffle, and the opposite wall of the battle has a substantially deep notch 30 opening to its front edge. It will be seen that the inlet baffle 13 defines a tortuous flow path for gases entering the expansion chamber, whereby such gases are divided into divergent streams that are caused to flow through the expansion chamber toward the outlet opening 19 along paths of unequal length.

Before entering the outlet opening, however, the gases must traverse a further tortuous path defined by the second bafiie I1 4. The second bafile can be formed from a single piece of sheet material to have two main wall portions 3'1 and 32 that are at an obtuse angle to one another, both provided with numerous perforations. The larger wall portion 31 is disposed parallel to the front and re'ar walls of the expansion chamber, behind the inlet opening and about on the plane of the shell rims. The portion 33 of the front wall of the expansion chamber that lies in front of said Wall portion 301. of the second bafile is stepped or rearwardly offset with respect to the remainder of the expansion chamber front wall to cobperate with the baffle wall portion 31 in defining a relatively narrow passage from which exhaust gases must pass through the perforations in the second baffle to reach the outlet opening 19.

The other wall portion 32 of the second baffle extends obliquely rearwardly and toward the inlet opening, and has its edges closely adjacent to the side and rear walls, respectively, of the rear shell member. Legs 34 that extend forwardly fro-m the free edges of the larger wall portion 31 underlie the side walls of the front shell member and are spot welded thereto to hold the second baffie in place. It will be seen that the second baffle extends across the expansion chamber in such a manner that it must be traversed by all gases flowing from the inlet opening 6 to the outlet opening 19.

The outlet tube 8 has a small bend 35 in its medial portion to dispose its opposite end portions at an obtuse angle to one another. This angle is complementary to the angle between the

rear wall portions

20 and 21 of the expansion chamber so that in one rotational position of the outlet tube the axis of its downstream or rear end portion can be parallel to the axis of the expansion chamber inlet opening. Near its front end the tube has a radially outwardly projecting circumferential flange 36 that can be defined by a crimp, and the front end portion of the tube is receivable in the outlet opening 19 with this flange overlying the rear wall portion 2 1 of the expansion chamber.

Overlying the flange 36 is a plate 37 in which there is a hole that closely fits around the tube, and said plate is secured to the wall portion 21, as by means of sheet metal screws 37, to cooperate with the flange 36 in holding the tube in place. It will be observed that loosening of the sheet metal screws 37 allows the tube to be adjustingly swiveled to accommodate it to a variety of different installation conditions and circumstances.

A plain tube or duct secured to the expansion chamber to direct gases rear-wardly in the maner of the tube 8 would actually intensify the exhaust noise of the engine, partially cancelling the silencing effects of the expansion chamber. However, the outlet tube 8 of this invention has in it the bafiie 15 which cooperates with the tube to define a pair of laterally

adjacent passages

38 and 39, one of which is effectively shorter than the other, said baflie providing a wall common to those two passages and which is apertured at its downstream end to permit communication between the passages. With the arrangement of this invention the outlet 8 does not diminish the silencing effects of the expansion chamber and causes no appreciable diminution of engine power output.

The baffie 15, which is flat and rectangular, extends lengthwise in the outlet tube and has its upstream end a little forward of the bend 35 in the tube while its downstream end is flush with the rear end of the tube. Transversely the baffle 15 extends substantially all the way across the tube and has its opposite edges spot welded to the wall of the tube at lengthwise spaced locations. The baffle thus cooperates with the tube in defining the pair of

p'a's's'ages

38 and 39 therein.

The faces of the baiile are perpendicular to the plane that contains the axes of the obliquely angled end portions of the tube, and the baffle is so disposed in the tube as to have its faces at acute angles to both of those axes; hence the passages 6b and 39 are of changing cross-section-a1 areas along their lengths, the passage 38 being of generally diminishing cross sectional area along the direction of gas flow and the passage 39 being of generally increasing cross-sectional area along said direction. Further to increase the effective cross-sectional area of the downstream end portion of the passage 39, the tube has a substantially large notch 42 opening to its rear end, at the side of the tube that defines the passage 39 and opposite the downstream end portion of the baffle 15, so that there is, in effect, no definite end to that passage.

The passage 38 like-wise has, in effect, an indefinite terminus, owing to the presence of a number of apertures 43 in the baffle 15, near the discharge end of the tube, which provide for a certain amount of communication between the

passages

38 and 39. It has been found that best results are obtained when these apertures are elongated lengthwise of the tube, as shown.

From the foregoing description taken with the accompanying drawings it will be apparent that this invention provides an exhaust outlet tube for a single cylinder internal combustion engine exhaust system by which exhaust gases can be discharged in a desired direction and to a desired location without any increase in the noise level of the exhaust system and without causing undue loss of engine power.

What is claimed as my invention is:

1. An exhaust mufller for an internal combustion engine having a cylinder with an exhaust port in a wall thereof, said mufller comprising:

(A) means defining an expansion chamber having spaced apart first and second wall portions,

(1) the first wall portion having an inlet opening therein and being adapted to be clamped against said wall of the engine cylinder with the inlet opening in registry with the exhaust port of the engine, and

(2) the second wall portion having an outlet opening therein;

(B) baflle means in the expansion chamber defining a plurality of tortuous paths for gases flowing from the inlet opening to the outlet opening;

(C) an out let tube;

(D) means mounting the outlet tube on the second wall portion of the expansion chamber with one end of the tube in registry with the outlet opening so that the tube receives exhaust gases from the expansion chamber and determines the direction of their discharge; and

(E) means to silence the discharge of exhaust gases from the tube comprising:

(1) a baflle in the tube extending lengthwise in its downstream end portion and dividing said portion of the tube into two lengthwise extending passages, one of which is generally convergent and the other of which is generally divergent toward the downstream end of the tube, said baflle having apertures in its downstream end portion, and

(2) the wall of the tube having a notch extending in from its discharge end and at its side that defines said other passage.

2. The exhaust muffler of claim 1, further characterized by:

(A) said first and second wall portions of the expansion chamber being disposed at an obtuse angle to one another such that the axes of the inlet and outlet openings diverge outwardly of the expansion chambers;

(B) the outlet tube being medially bent to dispose its end portions at an obtuse angle to one another substantially equal to said angle between the wall portions; and

(C) said means mounting the outlet tube on the second wall portion providing for adjusting rotation of the upstream end portion of the tube about its axis to enable the downstream end portion of the tube to be disposed in any of a number of different positions, in one of which it has its axis parallel to that of the inlet opening.

3. The exhaust mufller of claim 1, further characterized by:

said baffie comprising an elongated flat plate having its surfaces oblique to the axis of the downstream portion of the outlet tube.

4. The exhaust mufller of claim 3, further characterized by:

the apertures in said baflle being elongated in the direction lengthwise of the plate.

5. An exhaust mufller for an internal combustion engine having a cylinder with an exhaust port in a wall thereof, said mufller comprising:

(A) means defining an expansion chamber having (1) an inlet opening adapted to register with an exhaust port in an engine cylinder, and

(2 an outlet opening spaced from the inlet openmg and so oriented that gases emerging from the expansion chamber therethrough flow in a different direction than that in which they entered the inlet opening;

(B) baflle means in the expansion chamber defining a tortuous path for gases flowing therethrough from the inlet-opening to the outlet opening; and

(C) means for directing gases issuing from the outlet opening to a zone spaced therefrom, said means comprising:

(1) an outlet tube bent medially of its ends to dispose its end portions at an obtuse angle to one another,

(2) means mounting the outlet tube with one of its ends in registry with the outlet opening,

(3) a substantially rectangular flat baflle plate in the outlet tube with one of its ends near the other end of the outlet tube, the other end of the baflle plate being near the bend in the tube and the baflle plate having its surfaces oblique to the axis of the tube portion in which it is disposed so as to divide said portion of the tube into a pair of passages, one of which generally converges and the other of which generally diverges toward said other end of the tube,

(4) said baflle plate having lengthwise elongated apertures in its first mentioned end portion, and

(5) said tube having a notch opening to its said other end in the wall portion thereof that defines said other passage, opposite the baflie plate.

6. The exhaust mufller of claim 5 wherein said outlet opening is formed in a substantially flat wall portion of the expansion chamber, further characterized by said 35 means mounting the outlet tube comprising:

(A) a radially outwardly projecting circumferential flange on the outlet tube near the first mentioned end thereof, said flange overlying said wall portion of the expansion chamber;

(B) a substantially flat retaining plate having an aperture therein through which the tube is receivable; and

(C) means releasably securing the retaining plate to the expansion chamber with the retaining plate overlying said flange and said wall portion, said last named means providing for rotational adjustment of the outlet tube to dispose its said other end in any of a number of different positions.

7. An exhaust muffier for an internal combustion engine having a cylinder with an exhaust port in a wall thereof, said mufiler comprising:

(A) connected body and cover members forming an expansion chamber with a pair of opposite walls,

(1) one of said walls having spaced apart first and second wall portions, the former having an inlet opening therein and the latter having an outlet opening therein,

(2) the first wall portion being adapted to be clamped against said wall of the engine cylinder with the inlet opening in registry with the exhaust port of the engine;

(B) baflle means in the expansion chamber dividing the interior thereof into an inlet compartment to which the inlet opening leads and an outlet compartment from which the outlet opening leads;

(C) an outlet tube; and

(D) means mounting the outlet tube on said second wall portion with one end of the outlet tube in registry with said opening, so that the tube receives the exhaust gases leaving the expansion chamber and determines the direction of their discharge.

8. The exhaust mufiler of claim 7, wherein said first and second wall portions are disposed at an obtuse angle to one another and wherein said outlet tube has a medial bend that disposes its end portions at an angle to one a 7 another substantially equal to said obtuse angle, further characterized by said means mounting the outlet tube comprising:

(A) a crimp in'the outlet tube near said one end thereof defining a radially outwardly projecting flange around the outlet tube;

(B) a retainer having an aperture therein in which the outlet tube is receivable with a substantially close fit; and

(C) releasable meanssecuring the retainer to the second wall portion in overlying relation to the latter, for holding the retainer with the crimp confined between it and the second wall portion, release of said last named means enabling the tube to be rotated to dispose its other end portion in any of a number of positions, in one of which the axis thereof is parallel to the axis of the inlet opening.

9. An exhaust outlet tube for an internal combustion engine exhaust system, said outlet tube having an upstream end portion into which exhaust gases can flow and a downstream end portion from which exhaust gases can be discharged in a desired direction and to a desired zone, said outlet tube being characterized by:

(A) baffle means in the tube cooperating with it to de- (A) said baflie means comprising a substantially fiat plate which extends transversely across the tube and lengthwise therein at an inclination to the axis of the downstream end portion of the tube so that said one passage converges toward its downstream end and said other passage diverges toward its downstream end; and

(B) the downstream end portion of the tube having a substantially large notch in the wall portion thereof that defines said other passage, opposite the baffle, whereby the downstream end of said other passage is disposed a distance in the upstream direction from the downstream end of the first designated passage,

11. The exhaust outlet tube of claim 10, further characterized by? e the apertures in the bafile means being elongated in the direction'lengthwise of the tube.

References Cited UNITED STATES PATENTS FOREIGN PATENTS 354,913 6/ 1922 Germany. 410,247 5/ 1934 Great Britain. 475,047 10/ 1952 Italy.

514,686 2/1955 Italy.

ROBERT S. WARD, 1a., Primary Examiner.