US3168936A

US3168936A - Muffler for small internal combustion engines

Info

Publication number: US3168936A
Application number: US233005A
Authority: US
Inventors: Gordon Douglas
Original assignee: Briggs and Stratton Corp
Current assignee: Briggs and Stratton Corp
Priority date: 1962-10-25
Filing date: 1962-10-25
Publication date: 1965-02-09
Anticipated expiration: 1982-02-09

Description

MUFFLER FOR SMALL INTERNAL COMBUSTION'ENGINES Filed Oct. 25. 1962 D. GORDON Feb. 9, 1965 2 Sheets-Sheet 1 r II III I I I!!! I .lllll 77M) auglqs Gordan dthonm D. GORDON 3,168,936

MUFFLER FOR SMALL INTERNAL comsusnou ENGINES Feb. 9, 1965 2 Sheets-Sheet 2 Filed Oct. 25, 1962 dmchwfimj 01.1255 5 dan United States Patent 0 M This invention relates to mufilers for internal combustion engines and refers more particularly to a simple,

compact and inexpensive mufller which is especially suitable for single cylinder internal combustion engines of the type used on lawn mowers, garden tractors and the like.

The general object of this invention is to provide a mufiler for a single cylinder internal combustion engine which is not only simple and inexpensive in construction but which also affords the advantage of incorporating adjustable means for causing exhaust gases issuing from the mufller to be discharged in any selected one of a number of different directions.

Thus it is an important object of this invention to provide a muffler which is especially well adapted for the small engines commonly used on power lawn mowers, garden tractors, rotary tillers and the like, wherein the engine is often so installed as to be closely adjacent to other parts ofthe apparatus against which exhaust gases should notimpinge, the mufiler of this invention being particularly versatile for such applications because it incorporates readily adjustable means for diverting exhaust gases away from those parts of the installation that should be protected from them.

It is another and more specific object'of-this invention to provide a mufiler of the character described having a simple deflector for directing discharged exhaust gases in any selected one of a number of different directions, which deflector comprises a pan-like stamping secured to the body of the muffier by means of a single sheet metal screw or the like.

Another object of this invention is to provide a mufiler of the character'described which can be inexpensively made of only a few relatively simple stamped parts and whichis, moreover, unusual and very attractive in appearance.

Still another object of this invention is to provide a mufiler for small single cylinder engines, comprising a bafile member and a pair of complementary shell members which cooperate to define an expansion chamber in which the bafile member is located, wherein the bafile member performs both an acoustical function in causing gases to follow a tortuous path through the expansion chamber and a structural function in providing support and reinforcement to opposite walls of the expansion chamber. V

A further object of this invention is to provide a mufiler of the character described which is relatively short in the direction of axial flow of gases out of the exhaust pipe 'and into the mufiler and which is therefore very well adapted to single cylinder internal combustion engines which are installed on various devices wherein overall compactness of the power plant is highly desirable.

It is also a specific object of this invention toprovide a muffler of the character described comprising a bafile, member and a pair of complementary shell members which define a main expansion chamber in which the baflle member ishoused, wherein the shell members are 3,1683% Patented Feb. 9, 1955 member serves to reinforce'the shell members against the comprissive forces exerted by the bolts.

With the above and other objects in view which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiments of the herein disclosed invention may be made as come within the scope of the claims.

The accompanying drawings illustrate several complete examples of the physical embodiments of the invention constructed according to the best modes so far devised for the practicalapplication of the principles thereof, and in which:

FIGURE 1 is a front elevation view of a muffler embodying the principles of this invention, with a portion thereof cut away, the mufiler being shown installed on a single cylinder internal combustion engine, only a part of which is illustrated;

FIGURE 2 is a sectional view taken on the plane of the line 22 in PTGURE 1;

FIGURE 3 is a disassembled perspective view of the muffler shown in FIGURE 1;

FIGURE 4 is a perspective view of a modified form of the deflector member of the muffier of this invention;

FIGURES 5a5d are fragmentary plan views showing the several different directions in which exhaust gases can be discharged from the muffler of this invention by different adjustments of the deflector member shown in FIGURES 1-3 and by replacing said deflector member with that shown in PTGURE 4;

FIGURE6 is a fragmentary front elevation view of a muffler of this invention, with a portion thereof cut away, incorporating a modified form of bafile member; and

FIGURE 7 is a perspective view of the baffle member of themuflier shown in FIGURE 6. Referring now more particularly to the accompanying drawings, the muffler 5 of this invention is adapted to be carried on a short exhaust pipe 6 that projects from the cylinder of a single cylinder internal combustion engine 7 and which has flange or pad means 3 at its outlet end to provide for mounting the mufiler thereon.

In general, the mufiler 5 comprises complementary front and rear shell members l6 and 11 which cooperate to define an expansion chamber 12 that constitutes the main body portion of the mufiler, a bafile member 13 that is housed. in the expansion chamber, and a deflector 14 which is secured on the front of the expansion chamber and which cooperates with the front shell member ill to define an outlet chamber.

More specifically, the two shell members ill and 11 that comprise the expansion chamber 12 are generally rectangular in outline and are adapted to be formed as stampings, the front shell member being rather deeply drawn. The rear shell member is slightly dished but it has a flat marginal edge portion, 16 that extends around its entire periphery. It has a relatively large opening 1'7 near one corner thereof that provides an inlet port which is adapted to register with the mouth or outlet of the exhaust pipe 6 to which the mufiler is secured. The front shell member, which is substantially bowlshaped, has a' rim 19 around its edge that is clinched around the rim 16 of the rear shell member, as at 20, to secure the two shell members together in chamberdefining relationship. Y

The front wall of the expansion chamber 12 has a step 22 therein by which the portion 23 of the front wall that lies directly in front of the inlet port 17 is forwardly offset relative to the remainder of the front wall. The rearwardly offset portion 24 of the front wall has perforations 25 walls of the expansion chamber, the bafde also 2' (L7 therein that provide an outlet from the expansion chamber, and it will be noted that the area in which this outlet is located is spa ed a substantial distance to one side of the axis of the inlet port.

At its center the rearwardly offset portion of the front wall of the expansion chamber has a frustoconical forwardly projecting boss in I is received a sheet metal screw 27 or the like that secures the deflector mem ber I4 to the front shell member. The perforations are symmetrically arranged about the axis of this boss.

The barlle member extends between the front rear walls of the expansion chamber, substantially parc lel to the axis of the inlet port I7. Gases entering port are deflected by the baffle in a direction that tends .to carry them illay from the perforations 25, and the baflle thus serves to define a tortuous flow path through the expansion chamber. t its By reason of the fact to opposite ends are engaged with the front and rear end serves to provide reinforcing support to the shell members and 11 which define that chamber.

In the embodiment of the invention illustrated in FIG- URES 1-3 the bafide comprises a tube having a generally diamond-shaped cross section, but with rounded corners, and having numerous perforations 29 in its wall. its inside diame or is substantially larger than the diameter of the inlet port 17, and it is of course disposed coaxilly with that port so that gases entering the port flow directly into the tubular member. Freferabry the adjacent longitudinal edges of the blank from which the tubular baffle is formed are left slightly spaced apart, rather than being connected with a seam, so as to define a narrow slit that extends along the length of the baflle and which is located at the side of the baflle member remote from the perforations 25. The slit 3% thus provides a major outlet from the tubular baflle, through which gases issue in a direction that tends to carry them away from the expansion chamber outlet.

The muffier is secured to the exhaust pipe 65 by means of a pair of bolts fill, each of which extends through coaxial holes 32 and33 in the front and rear walls respectively of the expansion chamber and which are engaged in suitable tapped holes in the flange or pad means 8 on the exhaust pipe. The bolt holes 353 in the rear wall are spaced to diametrically opposite sides of the inlet port 17, and the bolts pass through the bafrle member, in engagement with its inside wall surface at opposite corners thereof. Hence the bolts not only secure the muffler to the exhaust pipe and hold the shell members against endwise separation but also confine the bafile against lateral displacement relative to the expansion chamber. The baffle of course serves as a stiffener or reinforcement that receives the inward compressive forces which the bolts impose upon the front and rear end walls of the shell.

Preferably the rear wall of the'expansion chamber is provided with an outwardly offset boss 34 around the inlet port 17 which defines a forwardly opening well in which the rear end portion of the baffle member is seated and which provides an external flat surface that seats on the mouth of the exhaust pipe 6 to make good sealing engagement therewith. By reason of the provision of thiswell and the engagement of the ends of the baffle against the front and rear end walls of the expansion chamber, the bame is held against displacement relative to the expansion chamber even before the mounting bolts 3 1 are installed.

In the embodiment of the invention illustrated in FIGURES 6 and 7 the baffle member 13 is an imperforate stamping formed from a rectangular blank and bent to a generally arcuate cross section with inwardly curled end portions 35. The baffle member 13' is installed in the expansion chamber with the bolts 31 passing through the sleeves 35 defined by its curled end portions, and with its arcuat'ely curved body portion at the side of the inlet port 1'7 which is nearest the perforations 2,5; and hence it serves as a deflector for gases entering the expansion chamber through the inlet port, by which such gases tend to be directed away from the outlet defined by the perforations 25 and are compelled to follow a tortuous path through the expansion chamber. Like the tubular baffle 13 in the previously described embodiment of the invention, the arcuate baffle plate 13' has its ends engaged with the front and rear walls of the expansion chamber and thus provides reinforcing support to those walls as well as being held in place by them.

Except for the inlet port 17, the bolt holes 32 and 33, and the perforations 25, the walls of the expansion chamber are imperforate, and hence all of the gases entering that chamber must leave the same by way of the outlet provided by the perforations 25, after pursuing a tortuous flow path through the chamber in the course of expansion therein.

The deflector member 14 is substantially rectangular and pan-like, and can thus comprise another inexpensive unitary stamping. In the embodiment of the invention illustrated in FIGURES l-3 the deflector member 14 has substantially narrow side walls 37 extending from three sides of its front wall 33, and is open at its fourth side to provide a discharge port 39. In the deflector member I l illustrated in FIGURE 4 the side walls 37 extend around all four edges of the front wall 33, and the discharge port 39 is defined by a narrow aperture in the front wall, near one edge thereof, which is elongated in the direction parallel to said edge.

In either case the deflector member has, at the center of its front wall 3% or 38, a forwardly concave dimple or boss 31 in which is received the sheet metal screw 27 by which the deflector member is securedto the front wall of the expansion chamber. The deflector member is held in place with the rear edges of its side walls engaging the front wall of the expansion chamber around the perforated area thereof, and with its front wall thus spaced from and substantially parallel to the rearwardly offset portion 24 of the front wall of the expansion chamber.

The deflector member cooperates with the front shell member Ill in defining an outlet chamber from which exhaust gases can be discharged in any selected one of several different directions. The wall portion 24 in which the perforations 25 are located is common to both the xpansion chamber and the outlet chamber, and said chambers are communicated with one another through those perforations. Because the outlet ohamberis substantially shallow, and its outlet is spaced to one side of the center of the group of perforations 25, gases flowing through the outlet chamber, from the perforations to the discharge port, are compelled to undergo repeated change of direction in the outlet chamber.

Although the deflector member is secured to the front shell member by only a single sheet metal screw through its center, the deflector member is normally held against rotation about that screw by reason of the engagement of one of its

side walls

37 or 37 against the step 22 in the front wall of the expansion chamber. However the screw 27 provides for rotational adjustment of the deflector member 14 to any one of three different positions, illustrated in FIGURE 5, namely with the discharge port located at one side of the mufier (FlGURE 5a) to direct exhaust gases sidewardly, at the top of the mufller (FIG- URE 5b) to direct discharged gases upwardly, or at the bottom on the muffler (FIGURE 50) to direct such gases downwardly. As an alternative, the deflector member 14 which has the discharge port 39 at the side thereof can be replaced by the modified deflector member 14 having the discharge port 39' in its front wall 33 to provide for forward or direct discharge of exhaust gases.

Attention is directed to the fact that the rectangular box-like configuration of the expansion chamber, together with the shallowness of the outlet chamber, causes the muffler of this invention to be relatively very compact in the direction of the axis of the exhaust pipe 6, so that it is well adapted to installations where power plant space is limited, as is often the case with devices powered by small single cylinder engines. The unusual and attractive appearance of the muffler of this invention is also note- Worthy.

From the foregoing description taken in connection with the accompanying drawings it will be apparent that this invention provides a muffler which is well adapted for small single cylinder internal combustion engines by reason of its compactness, simplicity and low cost, and which incorporates a readily adjustable deflector by which exhaust gases discharged from the muffler can be directed in any selected one of a number of different directions.

What is claimed as my invention is:

1. In a muffler of the character described:

(A) means defining an expansion chamber having front, rear and side walls and which has its front and rear walls spaced apart by a distance substantially less than their smallest dimension so as to be substantially shallow,

(l) the front wall of said expansion chamber having stepwise displaced forwardly and rearwardly offset portions connected by a step portion,

(2) the rear wall having an inlet port substantially in axial alignment with the forwardly offset portion of the front wall, and

(3) the rearwardly offset portion of the front Wall being apertured to provide an outlet;

(B) baffle means in said expansion chamber, extending from the rear wall to the forwardly offset portion of the front wall and located adjacent to the inlet port, said baffle means cooperating with the stepwise offset of the front wall portions and with the axially displaced locations of the inlet port and outlet to compel gases flowing through the expansion chamber to undergo repeated changes in flow direction;

(C) means cooperable with the rearwardly offset front wall portion of the expansion chamber to define an outlet chamber which is communicated through said outlet with the expansion chamber, said last named means comprising a pan-like element having front and side wall portions and having a discharge port at one side thereof; and

(D) securement means fastening said pan-like element to the rearwardly offset wall portion of the expansion chamber with the rear edges of the side walls of the pan-like element engaging said rearwardly offset wall portion and with the discharge port spaced to one side of the outlet, said securement means providing for adjusting rotation of the pan-like element about an axis normal to the rearwardly offset wall portion and substantially centered with respect to said outlet, to a plurality of positions of the pan-like element, in each of which a side wall portion thereof cooperates with the step portion of the front wall of the expansion chamber to prevent rotation of the pan-like element out of such position, and in each of which positions of the pan-like element gases are compelled to undergo changes of direction in flowing from the outlet to the discharge port.

2. The muflier of claim 1, further characterized by the following: the side walls of the pan-like element extend only partway around the same so that the discharge port opens from one side of the outlet chamber defined thereby; and said fastening means comprises a single screw extending through substantially the center of the front wall of the pan-like element and through said rearwardly offset wall portion of the expansion chamber so that the pan-like element is adjustably rotatable about the screw to different positions, in each of which the outlet port opens in a different direction.

3. The mufiier of claim 1, further characterized by the fact that the side walls of the pan-like element extend entirely around the same and the discharge port is in the front wall of the pan-like element, near one of its side walls.

4. A muffler for an internal combustion engine, comprising: means defining an expansion chamber having spaced apart front and rear end walls and having an inlet port in its rear end wall, near one side of the expansion chamber, a portion of the front Wall of the expansion chamber near the opposite side thereof being apertured to provide an outlet through which gases entering the expansion chamber by way of the inlet port can leave the same after undergoing a change in flow direction therein, and said portion of the front wall being stepwise rearwardly offset relative to the remainder thereof; a panlike deflector having a front wall and side walls which extend rearwardly from its front wall and which are substantially narrow as compared to its front wall; fastening means securing said deflector to the apertured rearwarolly offset portion of the front wall of the expansion chamber with the front wall of the deflector overlying and spaced from said apertured wall portion and with the side walls of the deflector engaging said apertured wall portion to cooperate with the same in defining an outlet chamber; and said outlet chamber having an opening in one side thereof which provides a discharge port through which exhaust gases, entering the outlet chamber through said apertured wall portion, can leave the outlet chamber after undergoing a change in flow direction therein, and by which such exhaust gases can be discharged in a predetermined direction.

5. The muffler of claim 4, further characterized by: a bafiie in the expansion chamber having opposite end portions engaged with said front and rear walls to be supported by and to supportingly reinforce the same, said baffle extending along a line substantially parallel to the axis of the inlet port and being so arranged adjacent to that axis as to deflect exhaust gases entering the inlet port away from said apertured wall portion and thus compel such gases to follow a tortuous path through the expansion chamber.

6. The mufiier of claim 5, wherein said baffle comprises a tubular member having numerous openings in its wall, arranged coaxially with the inlet port and having an inside diameter larger than the diameter of the inlet port.

7. A muffler for an internal combustion engine having an exhaust pipe with mounting pad means at the mouth thereof, said mufiier comprising: complementary front and rear shell members cooperating to provide an expansion chamber having spaced apart front and rear walls, said rear wall having an inlet port therein, near one side thereof, which is adapted to register with the mouth of an exhaust pipe, and said front wall having perforations therein in an area near the opposite side thereof, said area being stepwise rearwardly offset from the remainder of the front wall to define a ledge-like wall portion; a baffle member in the expansion chamber, extending along the axis of the inlet port and disposed to divert exhaust gases entering the expansion chamber through the inlet port away from said perforations, said bafile having its ends engaged against the front and rear end walls of the expansion chamber to be confined against axial displacement thereby and to supportingly reinforce the same; a pair of bolts extending through the front and rear end Walls of the expansion chamber and lengthwise along the baffle, and engaged in the mounting pad means on the exhaust pipe to secure the muffler thereto, hold the shell members against separation, and confine the baffle against lateral displacement; a pan-like deflector having a front wall and side wall portions extending rearwardly from its front wall and which are substantially narrower than either dimension of its front wall; and a fastener securing said deflector to the expansion chamber with the front wall of the deflector spaced from and extending substantially parallel to said perforated area of the front wall of the expansion chamber and with the side wall portions of a the deflector extending rearwardly into engagement with the front Wall of the expansion chamber around the perforations therein to cooperate with the expansion chamber in defining an outlet chamber communi ated with the expansion chamber through said perforations, said fastener providing for adjusting rotation of the deflector about an axis transverse to its front Wall and spaced from its side Walls and disposing the deflector With one of its side Wall portions adjacent to said ledge-like Wall portion for cooperation therewith in normally preventing 10 rotation of the deflector; and said outlet chamber having a discharge port at one side thereof to which gases can flow from said perforations only after undergoing a change of flow direction in the outlet chamber and from Which gases are discharged in a direction depending upon 15 the position of rotational adjustment of the deflector.

8. The muffler of claim 7 further characterized by the fact that one of the end Walls of the expansion chamber is formed With an inwardly opening Well therein in which its adjacent end portion of the bafiie member is received and by Which the baffle member is confined against lateral displacement.

References Qited in the file of this patent UNITED STATES PATENTS 1,276,209 Gray Aug. 20, 1918 1,304,096 Redeker et al May 20, 1919 1,442,196 Truelson Jan. 16, 1923 2,975,854 Bakke et a1. Mar. 21, 1961 FOREIGN PATENTS 7,185 Great Britain of 1913

Claims

1. IN A MUFFLER OF THE CHARACTER DESCRIBED: (A) MEANS DEFINING AN EXPANSION CHAMBER HAVING FRONT, REAR AND SIDE WALLS AND WHICH HAS ITS FRONT AND REAR WALLS SPACED APART BY A DISTANCE SUBSTANTIALLY LESS THAN THEIR SMALLEST DIMENSION SO AS TO BE SUBSTANTIALLY SHOLLOW, (1) THE FRONT WALL OF SAID EXPANSION CHAMBER HAVING STEPWISE DISPLACED FORWARDLY AND REARWARDLY OFFSET PORTIONS CONNECTED BY A STEP PORTION, (2) THE REAR WALL HAVING AN INLET PORT SUBSTANTIALLY IN AXIAL ALIGNMENT WITH THE FORWARDLY OFFSET PORTION OF THE FRONT WALL, AND (3) THE REARWARDLY OFFSET PORTION OF THE FRONT WALL BEING APERTURED TO PROVIDE AN OUTLET; (B) BAFFLE MEANS IN SAID EXPANSION CHAMBER, EXTENDING FROM THE REAR WALL TO THE FORWARDLY OFFSET PORTION OF THE FRONT WALL AND LOCATED ADJACENT TO THE INLET PORT, AND BAFFLE MEANS COOPERATING WITH THE STEPWISE OFFSET OF THE FRONT WALL PORTIONS AND WITH THE ADXIALLY DISPLACED LOCATIONS OF THE INLET PORT AND OUTLET TO COMPEL GASES FLOWING THROUGH THE EXPANSION CHAMBER TO UNDERGO REPEATED CHANGES IN FLOW DIRECTION; (C) MEANS COOPERABLE WITH THE REARWARDLY OFFSET FRONT WALL PORTION OF THE EXPANSION CHAMBER TO DEFINE AN OUTLET CHAMBER WHICH IS COMMUNICATED THROUGH SAID OUTLET WITH THE EXPANSION CHAMBER, SAID LAST NAMED MEANS COMPRISING A PAN-LIKE ELEMENT HAVING FRONT AND SIDE WALL PORTIONS AHD HAVING A DISCHARGE PORT AT ONE SIDE THEREOF; AND (D) SECUREMENT MEANS FASTENING SAID PAN-LIKE ELEMENT TO REARWARDLY OFFSET WALL PORTIONS OF THE EXPANSION CHAMBER WITH THE REAR EDGES OF THE SIDE WALLS OF THE PAN-LIKE ELEMENT ENGAGING SAID REARWARDLY OFFSET WALL PORTION AND WITH THE DISCHAGE PORT SPACED TO ONE SIDE OF THE OUTLET, SAID SECUREMENT MEANS PROVIDING FOR ADJUSTING ROTATION OF THE PAN-LIKE ELEMENT ABOUT AN AXIS NORMAL TO THE REARWARDLY OFFSET WALL PORTION AND SUBSTANTIALLY CENTERED WITH RESPECT TO SAID OUTLET, TO A PLURALITY OF POSITIONS OF THE PAN-LIKE ELEMENT, IN EACH OF WHICH A SIDE WALL PORTION THEREOF COOPERATES WITH THE STEP PORTION OF THE FRONT WALL OF THE EXPANSION CHAMBER TO PREVENT ROTATION OF THE PAN-LIKE ELEMENT OUT OF SUCH POSITION, AND IN EACH OF WHICH POSITIONS OF THE PAN-LIKE ELEMENT GASES ARE COMPELLED TO UNDERGO CHANGES OF DIRECTION IN FLOWING FROM THE OUTER TO THE DISCHARGE PORT.