US3400784A

US3400784A - Muffler with tangential exhaust intake and porous ends

Info

Publication number: US3400784A
Application number: US505124A
Authority: US
Inventors: Shannon O Thrasher
Original assignee: Individual
Current assignee: Individual
Priority date: 1965-10-19
Filing date: 1965-10-19
Publication date: 1968-09-10
Anticipated expiration: 1985-09-10

Description

p 0, 1968 s. o. THRASHER 3,400,784

MUFFLER WITH TANGENTIAL EXHAUST INTAKE AND POROUS ENDS Filed Oct. 19, 1965 3 Sheets-Sheet 1 I N VENTOR. 5HANNON Q flan/m p 1968 s. o. THRASHER 3,400,784

MUFFLER WITH TANGENTIAL EXHAUST INTAKE AND POROUS ENDS Filed Oct. 19, 1965 3 Sheets-Sheet 2 00000000 ooOooNfiooooooo ooc -oooo00o0n oflocogooooo INVENTOR. 5e SHANNON Q Z PAJ /se p 1968 s. o. THRASHER 3,400,784

MUFFLER WITH TANGENTIAL EXHAUST INTAKE AND POROUS ENDS Filed Oct. 19, 1965 5 Sheets-Sheet 3 I N VE N TO R. S/MA/A/oW 0. 72/645558 United States Patent Oflice 3,400,784 Patented Sept. 10, 1968 3,400,784 MUFFLER WITH TANGENTIAL EXHAUST INTAKE AND POROUS ENDS Shannon 0. Thrasher, 7116 Laurel Canyon Blvd., North Hollywood, Calif. 91605 Continuation-impart of application Ser. No. 432,490, Feb. 15, 1965. This application Oct. 19, 1965, Ser. No. 505,124

21 Claims. (Cl. 181-40) ABSTRACT OF THE DISCLOSURE A muffler construction particularly suited for use with low power, 2-cycle internal combustion engines. The muffler comprises generally a cylindrical housing with highly porous ends and a tangential exhaust intake. In two species of the mufiier, sound deadening material is placed adjacent the ends within the housing and separated with a porous annular band concentric with the housing. In two other species a series of concentric annular configurations formed of pluralities of arcuate metal plates are mounted between the ends of the housing.

This is a continuation-in-part of the co-pending patent application Ser. No. 432,490 now abandoned, filed Feb. 15, 1965 relating to mufflers and more specifically to a novel muflier construction which is particularly adaptable to use with two-cycle internal combustion engines.

The engines employed to drive lawn mowers, chain saws, motorized racer carts and similar machines are usually of a low horsepower, two-cycle, internal combustion type. Although such engines are relatively inexpensive and have a low fuel consumption, they are extremely noisy in their operation. This is not only annoying to the operator of the machine employing a two-cycle engine, but also to others in or around the neighborhood of the machine.

It is well known that one of the primary sources of noise in a two-cycle engine is exhaust leaving the engine and repeatedly striking the atmosphere in compact volumes. To deaden or otherwise absorb such explosive sounds, it is of course desirable to include some sort of muffler on the exahust manifold of the engine. Unfortunately, however, commercially available mufflers develop relatively large back pressures which cannot be tolerated by low power two-cycle engines. Also, conventional mufflers usually include a relatively long, straight housing which is too large to be conveniently mounted on lawn mowers, chain saws and other similar machines employing two-cycle engines. Primarily for these reasons, such two-cycle engines usually do not include a muffler.

In view of this, it is an object of the present invention to provide a novel muffler construction which develops an extremely low back pressure and is therefore ideally suited to use with low power, two-cycle internal combustion engines Another object of this invention is to provide a mufller construction of the foregoing type which is extremely compact, lightweight, and readily attachable to the exhaust manifold of two-cycle engines commonly employed to drive lawn movers, chain saws, motorized racer carts, and similar machines.

A further object of this invention is to provide a novel muffler construction which not only develops a minimum back pressure but is also highly effective in its mufiling operation.

Still another object of this invention is to provide a novel muffler for two-cycle engines which is inexpensive to manufacture.

A still further object of this invention is to provide a mufiier which is easily assembled and disassembled for servicing and replacement of parts.

The foregoing as well as other objects and advantages of this invention may be more readily understood by reference to the following detailed description when taken with the drawings which illustrates different forms of muffler construction embodying the features of this invention.

In the drawings:

FIGURE 1 is a perspective view of one form of muflier of the present invention in combination with and connected to the exhaust port of a two-cycle internal combustion engine;

FIGURE 2. is a sectional view of the muffler taken along the line 22 in FIGURE 1, illustrating the inner construction of the mufllcr including an outer housing supporting a thin, porous, annular band between opposing layers of sound deadening material;

FIGURE 3 is a sectional view of the mufller taken along the line 3 3= in FIGURE 2 illustrating the manner in which the annular band is centered within the housing between the layers of sound deadening material;

FIGURE 4 is a fragmentary view of a portion of the annular band, illustrating its highly porous structure;

FIGURE 5 is a sectional view of a second form of muffler of the present invention illustrating the inner construction thereof;

FIGURE 6 is a partially sectioned top view of the form of mufiier illustrated in FIGURE 5;

FIGURE 7 is a perspective view of a third form of mutfier constructed in accordance with the present invention;

FIGURE 8 is a perspective View of the separate component parts of the muffler of FIGURE 7 including a cylindrical metal housing, a multiple ring configuration including a plurality of arcuate plates, and a top cover plate, and illustrates the manner of construction of the component parts and their mode of combination to form the muffler;

FIGURE 9 is a partially section top view of the muffler of FIGURE 7 with the cover plate removed to illustrate the inner construction of the mufiler and the position of the component parts as they await the receipt of an exhaust pulse;

FIGURE 10 is a top view similar to FIGURE 9 illustrating the position of the component parts as the mufiier receives an exhaust pulse;

FIGURE 11 is a fragmentary sectional view of a portion of the multiple ring construction of the muffler illustrating the means for pivotally attaching the arcuate plates within the housing;

And FIGURE 12 is a partially sectioned top view of a fourth form of muffler construction with the cover plate thereof removed, the fourth form being similar to the third form with shortened arcuate plates to allow free in and out swinging movement of the arcuate plates in response to exhaust gas flow within the mufller.

As previously mentioned, it is Well known that one of the primary sources of engine noise in two-cycle internal combustion engines is the repeated explosion of compact volumes of exhaust gases upon reaching the atmosphere. Therefore, to mufile and substantially climinaie such noises, it is necessary to break up or smooth out the compact volumes of exhaust gases prior to striking the atmosphere.

In conventional muffiers for four-cycle engines, this is accomplished by including either sound absorptive or reflective means within a relatively long, straight mufller housing. As previously indicated, however, such arrangements are unsuited to use with low power, two-cycle engines.

In the present invention, sound reflective and absorptive means are combined in novel manners into a small, circular, compact and lightweight assembly which provides an extremely high degree of sound mufliing while developing minimal back pressure. Because of its highly eflicient mufliing operation with low back pressure build-up, the muflier assembly is ideally suited to use with low horsepower, two-cycle internal combustion engines. Further, due to the lightweight, compact construction of the mufiler assembly, it is readily mounted and attached to the exhaust manifold of such engines for lawn mowers, chain saws, motorized racer carts and other similar small machines.

In general, the foregoing advantages are achieved in the present invention by providing means for circulating exhaust gases within a compact housing and venting the exhaust through layers of sound deadening material or other sound deadening means to atmosphere through relatively large openings in the housing. During the circulation of the exhaust gases, they lose some of their momentum and the compact volumes thereof are smoothed to provide a relatively continuous flow of exhaust gases through the muffler. The passage of the exhaust through the sound deadening means provides even further continuity of exhaust flow and effectively absorbs sound waves remaining in the exhaust. Since the exhaust leaving the mufiler is substantially free of concentrated volumes, it therefore produces minimal noise upon striking the atmosphere. Further, the venting of exhaust to atmosphere through openings which are large compared to the exhaust intake the muffier has been found in practice to result in the development of very low back pressures, particularly when compared with those developed in conventional mufflers.

Referring more specifically to the drawings, a mufller assembly possessing the foregoing features is represented generally by the numeral and is shown in FIGURE 1 in combination with a small, two-cycle engine 11. The muffler assembly 10 includes a relatively fiat, generally cylindrical metal housing 12 having highly porous ends 14 and 16 and a side exhaust intake 18 extending tangentially from the housing for connection to the exhaust manifold of an engine. Preferably, the open area of the porous ends 14 and 16 is substantially greater than the open area of the exhaust intake port. As previously indicated, this has been found to be extremely important to the development of low back pressures in the muflier assembly.

Within the housing 12, the ends 14 and 16 are covered by

layers

20 and 22 of a porous sound deadening and absorptive material, preferably glass-fiber reinforced plastic. The layers of sound deadening material are retained in place by thin,

scrcenlike retaining discs

24 and 26 which in turn engage opposite edges of a thin, flat, highly porous annular band 28. The band is stationed in line with the exhaust intake 18 and is preferably concentric with the circular inner surface of the housing. To provide such centering of the band 28, cars 30 extend out- 4 wardly from the outer surface of the band and engage the inside of the housing.

It is to be noted, that in the illustrated form of the invention, the end 14 of the housing is removable therefrom and forms a cap having an annular flange 32 overlying the outside of the housing. The removable nature of the end 14 allows the mutlier to be quickly assembled or disassembled for replacement and servicing of parts. In this regard, the muflier assembly is easily assembled by laying the housing on its side with the end 16 facing down. The layer 22 of sound deadening material is then introduced into the housing covering the lower end 16 with the porous retaining disc 26 overlying the layer. Next, the band 28 is inserted into the housing and centrally located by the ears 30 engaging the inside of the housing. Then the porous retaining disc 24 is rested on top of the band and the layer 20 of sound deadening material stationed thereover. Finally, the removable end 14 of the housing is added and the combination tightly secured together by passing a bolt 34 upwardly through aligned holes in the ends of the housing and by tightening a nut 36 around the exposed threaded end of the bolt. In this condition, the muffler assembly is ready for attachment to the exhaust manifold of an engine to muflie exhaust noises.

In operation, high velocity pulses of exhaust gas from the engine enter the mufiler assembly 10 through the intake 18 and are tangentially received by the housing 12. Because of the circular nature of the housing, the exhaust gases are caused to travel in a circular path around the inside of the housing. Since the gases naturally follow the path of least resistance, they initially circulate in the annular area between the band 28 and the inside of the housing rather than passing through the pores in the band and in the retaining

discs

24 and 26. As the exhaust pulses travel in this circular path, they lose some of their momentum and the concentrated volumes of exhaust are smoothed out. As the exhaust gases circulate past the intake port, the high velocity thereof creates a pressure drop which effectively draws the exhaust gases from the engine. Then, as the exhaust gases lose some of their momentum, they travel through the pores in the band into the center of the housing and outwardly through the porous retaining discs into the layers of sound deadening material. The sound deadening material functions to further retard and sound dampen the exhaust gases which are then vented in a relatively continuous stream to the atmosphere through the porous ends of the housing. Due to the continuity of the exhaust gas flow to the atmosphere, the exhaust gases do not create explosive sounds upon reaching the atmosphere. In this manner, the muffler assembly effectively reduces exhaust noise to produce materially quieter engine operation.

As previously indicated, it has been found in practice that the circulation of exhaust gases and subsequent venting to atmosphere through large open areas, relative to the size of the exhaust intake, develop extremely low back pressures in the muffier assembly. Therefore, the mufller assembly is ideally suited for use with low power, two-cycle internal combustion engines.

In the foregoing, the assembly 10 has been described as being particularly useful as a mutiler for two-cycle engines. It should be noted in passing, however, that the assembly is also useful as an air filter for the air intake to a carburetor. In such an arrangement, the intake 18 is connected to the air intake port of the carburetor. As suction is developed in the intake port, air from the atmosphere is drawn in concentrated volumes through the porous ends 14 and 16 of the housing 12, filtered by the sound deadening material, and passed into the center of the housing. The air then circulates around the housing where the concentrated volumes are smoothed and then pass into the carburetor through the intake 18.

A second form of mufller construction is illustrated in FIGURES 5 and 6. In outward appearance, ease of assembly, and general principle of operation, the second form is very similar to the mufller 10. Therefore, the alternate form is represented by the numeral and parts thereof similar to those of the muffler 10 identified by like reference numerals with a prime notation.

The muffler assembly 10' includes a relatively flat, generally cylindrical metal housing 12 having a side exhaust intake 18' extending tangentially from the housing for connection to the exhaust manifold of an engine. The housing 12 also includes an open end 38 and a closed end 40 including a plurality of holes 42 each having a sleeve 44 extending therearound and inwardly therefrom.

The open end 38 of the housing is covered by a cap 46 releasably secured to the housing by a bolt 34'. The bolt 34 passes through aligned holes in the closed end 40 and the cap 46 and receives a nut 36' to lock the mufiler together. Similar to the closed end 40, cap 46 includes a plurality of holes 48 each having a sleeve 50 extending therearound and inwardly therefrom toward the middle of the housing. The open area of the

holes

42 and 48 is substantially greater than the open area of the exhaust intake 18'. As in the muffier 10, this means that the exhaust gases are vented to atmosphere through an open area which is larger than the exhaust intake to aid in minimizing the back pressure developed in the muffler 10'.

Within the housing 12', the end 40 and the cap 46 are covered by

layers

52 and 54 of a porous sound deadening and absorptive material, preferably glass-fiber reinforced plastic. The

layers

52 and 54 surround the

sleeves

44 and 50 which prevent the material from blowing out of the mutller during operation. The

layers

52 and 54 are retained in place by thin, highly porous,

circular retaining discs

56 and 58, which press against their inner surfaces and against the inner ends of the

sleeves

44 and 50 respectively.

The

discs

56 and 58 form parts of two groups of similar porous discs 60 and 62. The groups 60 and 62 include

circular discs

56, 64 and 66, and 58, 68 and 70, respectively. Corresponding discs of each group are of similar construction, each including a slightly recessed, fiat, circular central portion 72, and a fiat, annular outer portion 74 connected to the central portion by an outwardly inclined, annular, connecting portion 76 and engaging the circular inner surface of the housing 12'. As illustrated most clearly in FIGURE 5, the radial dimension of the central portion 72 is different for each disc of each group 60 and 62. In particular, the central portion of the

discs

56, 64 and 66, are of slightly increasing radial dimension as are the central portions of the discs 58, 68 and 70. The discs of each group, therefore, fit into each other with the outer edge of the central portion of the discs 64 and 68 engaging the inclined connecting portions of the

discs

56 and 58, respectively, and the outer edge of the central portion of the discs 66 and 7t) engaging the inclined connecting portions of the discs 64 and 68, respectively.

The inclined connecting portions of the discs 66 and define seats for the upper and lower edges of a thin, flat, annular band 77, preferably including a multiplicity of openings 78. The discs 66 and 70 support the band 77 concentric with the circular inner surface of the housing 12' and in general alignment with the intake 18', such that the band divides the housing 12 into an annular outer compartment 80 and a circular inner compartment 82.

The operation of the form 10' is similar to the muffler 10 in that high velocity pulses of exhaust gas from the engine enter the mufiler assembly 10' through the intake 18' and are tangentially received by the housing 12'. Because of the circular nature of the housing, the exhaust gases are caused to travel in a circular path around the inside of the housing within the compartment 80. Since the gases naturally flow the path of least resistance, they initially circulate in the annular compartment rather than passing immediately through the openings in the band 77 and in the discs 66 and 70.

As the exhaust gases circulate past the intake port 18, the high velocity thereof creates a pressure drop across the intake port which effectively draws or pumps the exhaust gases from the engine.

Similar to the mutfier 10. as the exhaust pulses travel in the circular path within the compartment 80, they lose some of their momentum and the concentrated volumes of exhaust are smoothed out. However, because the band 76 has fewer openings than the porous band 28, the gases circulate longer in the outer compartment 80 of the muffler 10 and lose more of their momentum before passing through the openings 78 into the inner compartment 82.

From the inner compartment 82, the gases pass to the groups of discs 60 and 62. Some gases also flow directly from the outer compartment to groups 60 and 62 rather than passing into the inner compartment. In the group 60, the gases are successively constrained to flow through the pores of the

discs

56, 64 and 66, and hence, through the sleeves 44 to atmosphere. In group 62, the gases are successively constrained to flow through the pores of the discs 58, 68 and 70, and hence, through the sleeves 50 to atmosphere. This causes the gases to be deflected, slightly contracted then expanded, and has the effect of breaking up any concentration of exhaust gases such that the gases flow smoothly and continuously through the

holes

42 and 48 to atmosphere.

In the housing, some of the gases passing through the pores of the

discs

56 and 58, strike the

layers

52 and 54. A certain amount of these gases are immediately reflected back through the discs and eventually pass through the

sleeves

44 and 50 to atmosphere. Certain others of these gases enter the porous sound deadening and absorptive material, circulate therein and then return through the

discs

56 and 58 to atmosphere through the

sleeves

44 and 50. In this manner, the material layers 52 and 54 act as buffers and sound dampening means to further produce continuous gas fiow through the muffler 10'.

Due to the continuity of gas flow to atmosphere, the exhaust gases do not create explosive sounds upon reaching the atmosphere. In this manner, the mufiler assembly 10 effectively reduces exhaust noise to produce materially quieter engine operation.

A third form of mufiler construction is illustrated in FIGURES 7l1 and represented generally by the numeral 84. The muffler 84 includes a relatively flat, generally cylindrical metal housing 86 having a side exhaust intake 88 extending tangentially from the housing for connection to the exhaust manifold of an engine. The housing 86 also includes an open end 90 and a closed end 92 including a plurality of holes 94, each having a sleeve 96 extending therearound and inwardly therefrom. The holes 94 are spaced from each other and arranged in a circular configuration closely about a central opening 98 in the closed end.

In addition to the plurality of holes 94, the closed end 92 includes a plurality of substantially concentric, generally circular arrays of dimples or depressions 100 in the inner surface of the closed end. In the illustrated form there are three arrays of different radial dimension and each include four dimples. The dimples of each array are equally spaced from adjacent dimples and are preferably radially aligned with corresponding dimples in the other arrays. As will be described hereinafter, the dimples 100 provide support for the sound deadening and dampening means Within the mufiler 84.

The open end 90 of the housing 86 is covered by a generally fiat cover plate 102 releasably secured to the housing by a bolt 104. The bolt passes through the central opening 98 in the closed end 92, a spacer sleeve 106 within the housing and through a central hole 108 in the cover plate to receive a nut 110 for locking the mufiler together. Similar to the closed end 92, the cover plate 102 includes a plurality of holes 112, each having a sleeve (not shown) extending therearound and inwardly therefrom toward the middle of the housing. The holes 112 are spaced from each other and arranged in a circular array closely around the central hole 108 in the cover plate 102.

In addition to the

holes

108 and 112, the cover plate 102 includes a plurality of substantially concentric, generally circular arrays of dimples or depressions 114 in the inner face of the cover plate. In the illustrated form, there are three arrays of different radial dimensions and each includes four dimples each corresponding to a different dimple in the closed end 92. The dimples 114 of each array are equally spaced from adjacent dimples and corresponding dimples of the arrays radially aligned with each other and directly opposite corresponding dimples 100 in the closed end 92 of the housing 86.

Within the housing 86, the corresponding

dimples

100 and 114 provide support for the sound dampening and deadening means of the mufiler 84. In the illustrated form, the sound deadening and dampening means comprises a plurality of substantially concentric,

annular configurations

116, 118 and 120. The

annular configurations

116, 118 and 128 are formed of pluralities of

arcuate metal plates

122, 124 and 126, respectively (here four each). At one end of each arcuate plate, lugs or ears 128 project outwardly in the plane of the arcuate plate and, as illustrated most clearly in FIGURE 11, are adapted to seat within corresponding

dimples

100 and 114 in the closed end 92 and cover plate 102 of the mufller 84.

The connection for the arcuate plates provided by the ears 128 and the corresponding

dimples

100 and 114 is such that each arcuate plate is mounted for swinging movement about one end (a fixed end) toward and away from the center of the housing 86. However, the arcuate plates comprising each of the

annular configurations

116, 118 and 120 are dimensioned such that the movable or free ends of the plates extend inwardly beyond, contact, and overlap the fixed ends of the adjacent arcuate P ates. Therefore, and as most clearly illustrated in FIGURES 9 and 10, the swinging movement of the arcuate plates within the housing 82 is somewhat limited. In particular, in swinging outwardly, the free ends of the

arcuate plates

122, 124 and 126 engage the fixed ends of adjacent arcuate plates while in swinging inwardly, the free ends of the

arcuate plates

122 and 124 engage the fixed ends of

arcuate plates

124 and 126, respectively (see FIGURE 10), the free ends of the arcuate plates 126 engaging the sleeves 96 surrounding the

holes

94 and 112.

Thus arranged, and generally speaking, the sound dampening means formed by the pluralities of

arcuate plates

122, 124 and 126 operate as pressure-sensitive valves for opening and closing in response to increases and decreases in gas pressure applied thereto and provide means for circulating and spiralling the exhaust gases around the inside of the housing and eventually outward through the

holes

94 and 112 in the ends of the mufiler 84 to atmosphere.

More particularly, when an exhaust gas pulse leaves the engine associated with the mufiler 84, it travels along the exhaust gas intake 88 and tangentially enters the housing 86. In front of the exhaust gas pulse there is a high pressure and behind the exhaust gas pulse there is a relatively low pressure or vacuum. The high pressure in front of the exhaust gas pulse causes the arcuate plates 112 successively to swing inwardly as the exhaust gas pulse follows the circular inner wall of the housing 86 and travels therearound. As the first arcuate plate 122 swings inwardly, a small portion of the exhaust gases pass through the opening between the free and fixed ends of the adjacent arcuate plates 122 and into the annular space 117 between the

configurations

116 and 118, the balance of the exhaust gas pulse continuing along the circular inner wall of the housing 86. The portion of the exhaust pulse moving along the circular inner wall of the housing 86 causes the next arcuate plate 122 to swing inwardly with a similar division of the exhaust gases occurring into the area 117. This process is repeated at each arcuate plate 122 as the exhaust gas pulse travels completely around the circular inner surface of the housing 86. In addition, the low pressure or vacuum following the exhaust gas pulse causes the arcuate plates 122 to swing outwardly after the pulse has past. Therefore, the arcuate plates 122 alternately swing inward and then outward in response to the travel of the exhaust gas pulse around the inner surface of the housing 86. In practice, since the exhaust gas pulses follow one after the other, the arcuate plates 122 effectively flutter, repeatedly swinging inwardly and outwardly in response to the series of exhaust gas pulses.

As in the other forms of the muffler, the exhaust gas pulses in circulating around the inner surface of the housing 86 travel past the intake 88. In so doing, the exhaust gas pulses create a vacuum at the end of the intake 88 which effectively draws or pumps gases from the engine and through the muffier 84. This has the dual elfect of aiding in the production of a low back pressure within the mufiler 84 and of effectively increasing the power and operating efficiency of the two-cycle engine connected to the mufller.

In addition, as the gases of the exhaust pulses travel around the inner surface of the housing 86 and cause an inward swinging of the plates 122, they lose much of their velocity and momentum. It is primarily the slower moving gases of reduced momentum which pass inwardly between the adjacent plates 122 as the plates swing inwardly.

The operation of the arcuate plates 124 in response to the portions of the exhaust gas pulses passing into the space 117 is the same as the arcuate plates 122. In particular, the exhaust gas pulses cause the arcuate plates 124 to alternately swing inwardly and outwardly as the exhaust pulses circulate within the annular space 117. As the arcuate plates 126 swing inwardly, small portions of the exhaust gases pass between the free and fixed ends of the arcuate plates into the annular space 119 between the

configurations

118 and 120. As before, as the gas pulses travel around the space 117 and cause an inward swinging of the plates 124, they lose much of their velocity and momentum. It is primarily the slower moving, reduced momentum gases which pass into the space 119.

Within the annular space 119, a similar operation occurs and the exhaust gases cause the arcuate plates 126 to alternately swing inwardly and outwardly as the exhause gases travel therearound and eventually into the center 121 of the housing 86 and outwardly through the

holes

94 and 112.

Accordingly, the

arcuate plates

122, 124 and 126 effectively flutter within the housing 86 in response to exhaust gas pulses and act as pressure-sensitive valves in opening and closing to divide, break up and smooth out the exhaust gas pulses which circulate around the inside of the housing, within the

annular spaces

117 and 119, and eventually pass outwardly from the mufller. In addition, as the exhaust gases comprising the pulses circulate within the housing 86, their velocity and energy is reduced. Therefore, after travel through the mufiler 84, the exhaust gases flow smoothly through the

openings

94 and 112 to atmosphere. Due to the continuity of gas flow through the

holes

94 and 112, the exhaust gases do not create explosive sounds upon reaching the atmosphere. In this manner, the mufiler 84 efiectively reduces exhaust noise to produce materially quieter engine operation. This, the muffler 84 accomplishes while creating a 9 minimum back pressure thereby allowing the mufiier to be ideally used with low horsepower, two-cycle engines.

A fourth form of the mufiier is illustrated in FIGURE 12. The fourth form is nearly identical to the muffler 84 illustrated and described in connection with FIGURES 7-11. Therefore, the mufiier illustrated in FIGURE 12 is represented by the numeral 84' and components thereof corresponding to components of the muffler 84 bear a like reference numeral with a prime notation.

In practice, the only difierence between the mufflers 84 and 84' is that the arcuate plates 122', 124' and 126 of the mufiler 84' are shortened so as not to overlap the fixed ends of the adjacent plates. Therefore, the arcuate plates are free tn swing inwardly and outwardly within the housing 86 into and out of the annular spaces between the circular inner wall of the housing, and the

configurations

116, 118 and 120. This reduces the contact and therefore the contact noise between the swinging free ends of the arcuate plates to lower the muffier noise level. This also has a practical effect of further lowering the back pressure developed by the mufiier in that larger effective paths are provided for the exhaust gases to the outlet ports defined by the

holes

94 and 112. In addition, there is a greater reduction of energy from the exhaust since each arcuate plate is allowed to swing more freely in response to the exhaust gases and in this manner to withdraw greater amounts of energy from the exhaust gases.

While the foregoing specification has described in some detail particular forms of the muflier assemblies, changes and modifications in design may occur to those skilled in the art without departing from the spirit of the present invention. It is therefore intended that the invention be limited in scope only by the following claims.

I claim:

1. A muffler comprising:

a generally cylindrical housing including a side, gas intake port and a substantially open top and bottom having an open area larger than said intake port;

layers of porous sound deadening material within said housing covering said top and bottom;

and a highly porous, annular band stationed within said housing between said layers of sound deadening material for circulating gases from said intake port around the circular inner surface of said housing, through said porous band, and outwardly through said layers of sound deadening material and said open top and bottom.

2. Amuffier comprising:

a pair of highly porous retainers over inner surfaces of said layers of sound deadening material;

and a highly porous, annular band stationed within said housing between said retainers for circulating gases from said intake port around the circular inner surface of said housing, through said porous band, and outwardly through said layers of sound deadening material and said open top and bottom.

3. A muffler comprising:

a hollow housing having a removable porous top, a

porous bottom, and a side intake port;

layers of sound deadening material within said housing covering said porous top and bottom;

a fiat, porous, annnular band stationed within said housing between said layers of sound deadening material for circulating gases from said intake port around the inside of said housing, through said porous band and outwardly through said layers of sound deadening material and said porous top and bottom;

and means for releasably securing said removable top to said housing.

4. A mufiler comprising:

a hollow, generally cylindrical housing having a removable porous top, a porous bottom, and a side intake port, the open area of said top and bottom being greater than said intake port;

a pair of flat retaining screens engaging the inner sides of said layers of sound deadening material;

a porous, annular band stationed between said retaining screens substantially concentric with said housand a bolt extending through said housing between said top and bottom to secure said removable top to said housing.

5. The mufiler of claim 4 wherein said sound deadening material is glass fiber.

6. A muflier comprising:

a hollow, generally cylindrical housing including a side exhaust intake port, an open end, and a closed end including a first plurality of holes, each having a sleeve extending therearound and inwardly therefrom;

a removable cap over said open end of said housing and including a second plurality of holes, each having a sleeve extending therearound and inwardly therefrom, the open area of said first and second plurality of holes being greater than the open area of said intake port;

first and second layers of sound deadening material over said closed end and open end respectively and surrounding said sleeves around said first and second plurality of holes;

first and second pluralities of porous discs spaced from and stationed one over the other and over said first and second layers respectively with outer discs of said first and second pluralities of discs adjacent the inner ends of said sleeves surrounding said first and second plurality of holes respectively;

and an annular band, centrally located within said housing and spaced from the inner walls thereof between said first and second plurality of discs in general alignment with side intake port and including a multiplicity of holes.

7. A mufiier comprising:

a hollow housing including a side exhaust intake port and a opposing ends each including a plurality of holes each having a sleeve extending therearound and inwardly therefrom, the open area of said holes being greater than the open area of said intake port;

first and second layers of sound deadening material over said ends of said housing and surrounding said sleeves;

first and second pluralities of porous discs spaced from and stationed one over the other and over said first and second layers respectively with outer discs of said first and second pluralities of discs adjacent the inner ends of said sleeves surrounding said holes in said opposing ends of said housing;

and a continuous band, centrally located within said housing and spaced from the inner walls thereof between sa-id first and second plurality of discs in general alignment with said side intake port and including a multiplicity of holes.

8. A muffler comprising:

a hollow housing including a side intake port and an end including a plurality of holes each having a sleeve extending therearound and inwardly therefrom, the open area of said holes being greater than the open area of said intake port;

a layer of sound deadening material over said end of said housing surrounding said sleeves;

a plurality of porous discs spaced from and stationed one over the other and over said layer of sound deadening material of said discs adjacent the inner ends of said sleeves;

and a continuous band stationed within said housing and spaced from the inner walls thereof in general alignment with said intake port with a continuous edge adjacent an inner disc of said plurality of porous discs.

9. A mufiier comprising:

a hollow housing including a side intake port and an end including a plurality of holes, the open area of said holes being greater than the open area of said intake port;

a layer of sound deadening material over said end of said housing;

a plurality of porous discs spaced from and stationed one over the other and over said layer of sound deadening material;

10. A mui'l'ler comprising:

a hollow housing having an exhaust gas intake port and an end including a plurality of holes;

a layer of sound deadening material over said end of said housing with openings communicating with said holes in said end;

means for circulating gases from said intake port around the inside of said housing and past said intake port including a continuous band stationed within said housing and spaced from the inner walls thereof and including a plurality of openings for passing said gases into the center of said band after circulating around said housing;

and a plurality of gas flow constraining means separated from each other between said band and said holes in said end of said housing for separately and successively constraining said gases as they flow from the center of said band to said holes in said housing.

11. A mufiler comprising:

and sound deadening means including a plurality of gas flow constraining means separated from each other between said band and said holes in said end of said housing for separately and successively constraining said gases as they flow from the center of said band to said holes.

, 12. A muffler comprising:

a hollow housing including an exhaust gas intake port;

a plurality of gas pressure sensitive valve means arranged in a circular configuration Within said housing for opening and closing in response to increases and decreases in the pressure of exhaust gases applied thereto;

and means within said housing for circulating exhaust gases from said intake port around the inside of said housing past the intake port and through said valve means to atmosphere.

13. A muffler comprising:

a hollow housing including a generally circular inner surface and an exhaust gas intake port leading from said inner surface;

and a plurality of gas pressure sensitive valve means arranged in a circular configuration within said housing for opening and closing in response to increases and decreases in the pressure of the gas applied thereto and including means for circulating exhaust gases from said intake port along said inner surface of said housing past the intake port and through said valve means to atmosphere.

14. A mufiler comprising:

a hollow housing including an exhaust gas intake port in one side and an end including a plurality of outlet holes;

and means for circulating exhaust gases from said intake port around the inside of said housing past said intake port, smoothing the flow of said exhaust gases, and venting said gases through said holes, said means including a plurality of arc-shaped members arranged in a generally circular configuration and each hinged at one end for swinging movement toward and away from the center of said configuration.

15. The niufiler of claim 14 wherein ends of adjacent arc-shaped members overlap each other.

16. A muffler comprising:

a hollow housing including an exhaust gas intake port in a side thereof and an end including a plurality of holes;

and means for spiralling exhaust gases from said intake port past around the inside of said housing past said intake port, smoothing the flow of said gases, and venting said gases through said holes, said means including a plurality of substantially concentric annular configurations each including a plurality of arcuate plates hinged at one end for movement toward and away from the center of said configurations.

17. The muffler of claim 16 wherein ends of adjacent arc-shaped plates overlap each other.

18. The mufller comprising:

a hollow housing including an exhaust gas intake port in a side thereof and opposite ends including pluralities of holes and circular arrays and dimples in the inner sides thereof, said dimples of each array being circumferentially spaced from each other and corresponding dimples in said opposite ends being aligned with each other;

and means for circulating exhaust gases from said in take port around the inside of said housing and past said intake port, smoothing the flow of said exhaust gases, and venting said gases through said plurality of holes, said means including an annular configuration of arc-shaped plates including projecting lugs fitting into corresponding dimples in said opposite ends for supporting said arc-shaped plates for swinging movement toward and away from the center of said configuration.

19. A muffler comprising:

a hollow housing including an exhaust gas intake port in a side thereof and opposite ends including pluralities of holes and pluralities of substantially concentric circular arrays of dimples in the inner sides thereof, said dimples of each array being circumferentially spaced from each other and corresponding dimples in said opposite ends being aligned with each other;

and means for circulating exhaust gases from said intake port around said housing and past said intake port, smoothing the flow of exhaust gases, and venting said exhaust gases through said plurality of holes, said means including a plurality of substantially concentric annular configurations of thin arc-shaped plates, each including projecting lugs fitting into corresponding dimples in said opposite ends for supporting said arc-shaped plates for swinging movement toward and away from each other.

13 20. The mufiier of claim 19 wherein said pluralities of holes are located in central portions of said opposite ends with sleeves extending inwardly from said opposite ends around said holes to act as stops for said arc-shaped plates. 21. The mufiier of claim 20 wherein ends of adjacent arc-shaped plates overlap each other.

References Cited UNITED STATES PATENTS ROBERT S. WARD, JR., Primary Examiner.

FOREIGN PATENTS France. France. Germany. Germany. Germany. Great Britain. Great Britain. Great Britain. Great Britain. Great Britain.