US3187837A - Free flow acoustic silencer constructed of resilient material - Google Patents

Description

June 8, 1965 c. G. BEECHING 3,187,837

FREE FLOW ACOUSTIC SILENCER CONSTRUCTED OF RESILIENT MATERIAL Filed Aug. 28, 1965 3 Sheets-Sheet l 26 l5 I6 I I0 25 mun/roe CHARLES G. BEECH ING MATERIAL June 8, 1965 c. G. BEECHING FREE FLOW ACOUSTIC SILENCER CONSTRUCTED OF RESILIENT Filed Aug. 28, 1963 June 8, 1965 c. e. BEECHING FREE FLOW ACOUSTIC SILENCER CONSTRUCTED OF RESILIENT MATERIAL Filed Aug. 28, 1963 3 Sheets-Sheet 5 United States Patent Canada) Filed Aug. 23, 1%3, No. 3ll5,234

9 Claims. or. ran-es This invention relates to silencers or mufi'llers used to reduce the exhaust noise of internal combustion engines, and has particular reference to inboard marine installations, and to stationary installations.

This application is a continuation-in-part of my prior copending application, Serial No. 13,070, filed March 7, 1960, now abandoned.

It is possible by conventional means greatly to reduce exhaust noise. If silencing is by means of baliie plates, flaps, slits, and like devices, in mufflers of ordinary size having regard to the power of the motor, back pressure results. This causes material loss of power, rapid burning of exhaust valves, fouling, and other undesirable effects. With larger mufiiers, the undesirable effects are reduced but the expense is considerable. In either case, the useful life before replacement or repair may be short.

The objects of the invention are to produce a silencing device of cheap light construction which shall be free of the defects above.

in my mufiler silencing is accomplished by acoustic damping chambers, and it is provided that the exhaust gases flow sensibly unimpeded through the device, encountering only resistance of the order of that of the exhaust pipe itself. The design is adapted to cheap light mass production in natural or synthetic rubber, resilient plastic, or like material, non-corrosive, resistant to oil acid and the like, and having adequate heat-resistant properties. Construction in such materials is particularly suitable to marine installations where cooling water is discharged through the exhaust.

Other objects, advantages and details of the invention will be apparent as the description proceeds, reference being had to the accompanying drawings wherein several forms of the invention are shown. It is to be understood that the description and drawin s are illustrative only, and that the scope of the invention is to be measured by the appended claims.

In the drawings:

FIG. 1 is a side elevational view of one form of muffler embodying the invention.

FlG. 2 is a longitudinal sectional view of the muiiler shown in FIG. 1, the view taken on line A-A of FIG. 3.

FIG. 3 is an end elevational view of the muiller shown in FIGS. 1 and 2.

FIG. 4 is a side elevational View of a commercial mufiler embodying the invention.

FIG. 5 is a longitudinal sectional View of the muificr shown in FIG. 4, the view taken on line 5-5 of PEG. 6.

FIG. 6 is a transverse sectional view taken on line 6-6 of FIG. 4.

FIG. 7 is a longitudinal sectional view of another commercial muffler embodying the invention, the view taken on line 77 of FIG. 8.

FIG. 8 is a transverse sectional view taken on line 3-8 of FIG. 7.

In FIG. 1 the hollow body or shell indicated by the numeral 1 consists of the parts 2 and to be vulcanized or cemented at the joint ir In the embodiment now being described, the mufiler is constructed of plastic material, or of suitable natural or synthetic rubber.

The shell end walls 5 and 10 contain parts 29 and 36 generally 3 adapted adapted as shown to receive the exhaust pipe 6 and the tail pipe 7 respectively. Exhaust pipe 6 connects directly to the exhaust manifold of the internal combustion engine (not shown), and is of standard diameter as supplied or recommended by the manufacturer of the engine. The tail pipe '7 preferably may be somewhat larger than the exhaust pipe aforesaid. The parts 29 and 30 are aligned as shown.

The muflier is secured to the exhaust and tail pipes by conventional clamps 8 and 9. It will be understood that the tail pipe merely serves to lead the exhaust gases from the muffler to a suitable discharge point, and has no material effect upon the operation.

As shown in FIG. 2, the shell end walls 5 and 10 have shoulders formed at 11 and 12. Pieces l3, 14, 15, 16 and 26 are hollow cylinders of progressively diminishing length.

17 through 2d are partitions transverse of the length of the muffler shell 1 dividing the same internally into acoustic damping chambers 21, through 25. Referring to the partition 17, this is of disc shape having diameter equal to the inner diameter of the shell 1, less a suitable small clearance to facilitate assembly. It contains the opening 2'7, suitably circular, the area of which opening is not less than that of the inner diameter of the intake pipe e, or tail pipe '7, whichever may be greater. The opening 27 is disposed opposite the intake port 29 as shown. The succeeding partitions l 19, 20 are the same as, and interchangeable with, the partition 17, and the openings are aligned as shown.

Assembly is as follows. Cylinder 13 is inserted in the hollow shell portion 3 to bear against the shoulder 11 of the end wall in, and the disc 1'7 placed in position as shown in FIG. 2. Next the cylinder 14 is placed in position completing the assembly of the left hand portion 3 of the silencer. These parts are cemented or vucanized to one another.

In like manner, cylinder disc 20, cylinder 16 disc 3%, cylinder 15 disc 18, are progressively inserted in the right hand portion 2 of the shell 1, and cemented or vulcanized to form the right hand portion of the muffler.

The two completed sections are joined by inserting cylinder 14 into one portion, and sliding the other portion over that part of 1 5 now protruding, to form the joint 4, the whole being suitably vulcanized or cemented together.

it is seen that the mufder consists of the several chambers 21 through 25 of diminishing size, communicating by means of openings as 27.

The action is described with reference to FIG. 2. EX- haust gases flow in the manner indicated by the arrows, and it is seen that there is clear space, circular in section, throughout the length of the mulfier, the least diameter of which clear space is not less than the greater of the inside diameters of the exhaust pipe 6 or tail pipe 7.

Thus the mean pressure within my mufller will be less than the corresponding mean pressure in that part of the exhaust pipe immediately preceding the muffler; accordingly freedom from burned out exhaust valves, fouling and like effects will be as in an unmuliled engine with an open exhaust pipe. As well, the power will not be re duced from excessive back pressure.

The pressure in exhaust pipe d is pulsating violently, at frequency according to the explosions of the cylinders of the internal combustion engine. Superimposed upon this primary wave are complex audible transients. The complex entering pressure wave expands into chamber 21, and the lower frequencies and their harmonics tend to be damped. As the discharge proceeds from chamber to chamber higher frequencies are absorbed in a similar manner by the succeeding chambers of diminishing size. The result is that most of the audible frequencies have proarenas? gressively been damped, and while the discharge will still pulsate in pressure, the amplitude of the pulsation s materialiy reduced and, with it, the noise.

Silencing to an extent, will take place when exhaust gases are permitted to expand into a hollow shell, or enlarged exhaust pipe portion, without bathing. When apertured baffles are added, still further silencing occurs. The rnufiling action increases when the battles are transverse ported'partitions so spaced to define acoustic chambers as described.

The device described above employs a pliable resilient shell which, in combination with the above features, provides further damping. It is apparent that the pulsations of pressure within this shell are large, and consequently there is deformation of the shell, and difficulty in providing attachment of the baffies to the shell without making the shell of undue thickness, and consequentlyot rigidity such as to impair flexibility. This diificulty I have overcome in the manner above described, namely by providing cylindrical spacers separating the baffles. As will be clear from FIG. 2, this arrangement acts to form a composite shell composed of the outer part, and the inner spacing cylinders as 15. In this way I am able to provide a composite of suitable total wall thickness. Moreover, manufacture and assembly are thereby facilitated.

Using this construction, and with total thickness of the composite wall as small as three sixteenths of an inch, I am able to make a composite shell sufiiciently thin to have the required flexibility and, at the same time, I overcome the difficulty of rigid attachment of the partitions, or baffles, to the wall.

PlGS. 4-6 shows one commercial form of mufller embodying the invention. The respective component parts are molded from suitable resilient material, such as natural or synthetic rubber, that is non-corrosive, resistant to oil, acid and the like, and has adequate thermal properties.

Outer shell 35, as illustrated, is formed from two like parts 36 and 37, the two parts being cup-shaped and provided at their open ends with flanges 38 and 39 adapted to be secured together in final assembly. End walls dill and 41 of parts 36 and 37 have central circular ports 4-2 and 43, the ports being surrounded on the external faces of the walls by tubular portions 44 and 45 adapted to be connected respectively to exhaust and tail pipes (not shown).

Referring to FIGS. and 6, a plurality of chamberforming units of resilient material are disposed within shell 35. The chamber-forming units vary in size, and so will be described separately. Each unit is cup-shaped, as will be seen.

Chamber-forming unit Sti is located at the left-hand end muffler adjacent end wall 469 having a port d2 that admits exhaust gases to the mufiler interior. 7

Unit 50 has a bottom portion 51 that serves as a transverse partition within shell 35 and a side wall 52 that serves as a spacer determining the axial length of chamber 53- formed by the unit. Bottom portion 51, best shown in FIG. 6, has an elongated opening 54, the shape of opening 54 in the illustrated embodiment being substantially oyal. The major axis of opening 54 is shown about equal in length to the diameter of bottom portion 51, although it may be somewhat shorter.

The area of the opening 54 is not less than the greater of the areas of ports 42 and 43 in the end walls of outer of the muffier shown in FIGS. 4 and 5, the end of the 7 shell 35, the areas of such ports usually being about the I same size.

Proceeding to the right, next adjacent chamber-forming unit 55 has bottom portion 56 and side wall 57, the length of side wall 57 being such that the over-all axial length of defined chamber 58 is somewhat less than that' of chamber 53. As shown, the length of side wall 57 is substantially equal to that of side wall 52; however, the axial length of larger chamber 53 is the distance between opening 42 and bottom portion 51. Thus, the same sized unit may be used for both chambers.

Bottom portion 56 of unit 55 has an opening 59 of substantially the same shape and size as opening 54- in preceding bottom portion 51, As will be seen, opening 59 preferably has aditlerent angular orientation than opening 54-.

Next adjacent chamber-forming unit 6h has bottom portion 61 and side wall 62, the latter having such length that defined chamber 63 has a smaller axial length than preceding chamber 58. Side wall 62, as shown, projects to the right beyond bottom portion 61, as shown at 62a, the extending portion serving as a spacer with respect to end wall 41 of the outer shell. 7

Bottom portion 61. of unit 6! has an elongated opening 64 of substantially the same size and shape as the previous openings 54.- and 59. The three openings are shown in superimposed relation in FIG. 6.

As shown in FIG. 6, the respective chamber-forming units 56, 55 and 6b in the illustrated commercial form are angularly oriented so that the major axes of the openings 59 and 6d dilfer from the major axis of the preceding openings by a predetermined angle. The angle illustrated is substantially sixty degrees. Thus, the majoraxis of opening 54 is shown disposed vertically, the axis of open ing 5) is disposed sixty degrees clockwise therefrom, and the axis of opening 64 is disposed sixty degrees clockwise from the axis of opening 59. It has been found that these angular orientations impart a rotary movement to gases passing through the muflier, and such rotary movement increases the effective length and the silencing quality of the muffler, and avoids objectionable back pressure.

In the commercial muffler described above, the outer diameter of shell 35 is six inches, and the respective axial lengths of the chambers 53, 58, 63 and rigl1t-hand chamber as are four inches, three inches, two and one-half inches and two inches. The diameter of end ports 42 and 43 is substantially three and one-eighth inches.

it has been found that a mufiier constructed to these dimensions is highly elfective from the standpoint of silencing and the prevention of objectionable back pressure.

FIGS. 7 and 8 illustrate another commercial embodiment of the invention, this form differing from the FIGS. 4-6 form only in the angular orientation of the respective chambenforrning units 70, 71 and '72. Here, the major axes of the elongated openings in the bottom portions of the units differ in orientation from that of the major axis of the preceding opening by ninety degrees. Thus, as shown, opening '73 in unit 7% has its major axis oriented vertically, and the major axis of following opening 74- is oriented ninety degrees clockwise, or horizontally. Opening 75 in unit 72 has its major axis oriented ninety degrees farther in clockwise direction, or vertically, the same as the axis of the first opening 7'3.

It is believed that the relative orientations of the openings shown in FIGS. 7 and 8 cooperate to impart an oscillating movement to the gases passing through the muftier. Such movement, as in the case of the rotary movement provided by the sixty degree differential, increases the effective length and silencing quality of the mufiler, and avoids objectionable back pressure.

Experimentation has shown that desirable results are achieved with angular differentials falling in the range of from one to ninety degrees.

From the above description it is thought that the construction and advantages of this invention will be readily apparent to those skilled in the art. Various changes in detail may be made without departing from the spirit or losing the advantages of the invention.

Having thus described the invention, what is claimed as new and desired to secure by Letters Patent is:

ll. A silencing device for attachment to the exhaust pipe of an internal combustion engine comprising:

an outer resilient shell of substantially uniform cross section having a side wall and end walls, one end ing an opening of substantially oval shape, the major wall ported and adapted for connection to the exaxis of said opening substantially equal in length to haust pipe aforesaid, the other end wall ported and the diameter of said bottom portion and the area of adapted for the connection of a tail pipe for egress said opening not less than the greater of the areas of exhaust gases, the shell fabricated in two parts of said ports in said shell end walls; to facilitate assembly, said two parts having open said chamber-forming units oriented in said shell so ends adapted to be joined after assembly, the angular position of the major axes of said oval transverse partitions within the shell to define chambers openings in successive chamber-forming units after of unequal size the largest said chamber being that the unit nearest the gas-admitting end wall diiters adjacent the end wall ported for the exhaust pipe from the angular position of the major axis of the as aforesaid, an opening in each said partition, each preceding oval opening by a predetermined angle. said opening having an area not less than the greater 4. The combination of claim 3 wherein said predeterof the internal diameters of the said exhaust and tail mined angle is substantially sixty degrees. pipes, the said openings aligned With one another 5. The combination of claim 3 wherein said predeterand with the end wall ports, mined angle is substantially ninety degrees. cylindrical spacers, of resilient material similar to that 6. The combination of claim 3 wherein said predeterof the outer resilient shell, for insertion within the mined angle falls in the range of from one to ninety outer resilient shell, the outside diameters of said degrees. spacers equal to the inside diameter of the outer shell, '7. A silencing device for attachment to the exhaust the axial length of the spacers such as to define the pipe of an internal combustion engine comprising: distance between said transverse partitions, an outer resilient shell having a side wall and opposite the outer resilient shell and the resilient spacers aforeend walls, one end wall having a port to admit exsaid comprising a composite shell of total thickness haust gases and the other end wall having a port to not less than three sixteenths of an inch. discharge said gases; 2. A silencing device for attachment to the exhau t chamber-orming units of resilient material within said pipe of an internal combustion engine comprising: shell defining chambers of progressively smaller size, an outer resilient shell having a side Wall and opposite the largest of said chambers being adjacent said gasend walls, one end wall having a central circular port admitting end wall, each chamber-forming unit cupto admit exhaust gases and the other end wall having shaped with the bottom portion thereof constituting a central circular port to discharge said gases, said a partition separating adjacent chambers and the side shell fabricated in two parts to facilitate assembly, wall thereof constituting a spacer determining the said two parts having open ends adapted to be joined axial length of the chamber formed by said unit, together; said side wall of said unit engaging the side wall of chamber-forming units of resilient material within said said shell;

shell defining chambers of progressively smaller size, the bottom portion of each chamber-forming unit havthe largest of said chambers being adjacent said gasing an elongated opening, the major axis of said openadmitting end wall, each chamber-forming unit cupin substantially equal in length to the diameter of shaped with the bottom portion thereof constituting said bottom portion and the area of said opening not a partition separating adjacent chambers and the side less than the greater of the areas of said ports in said wall thereof constituting a spacer determining the shell end Walls; axial length of the chamber formed by said unit, said chamber-forming units oriented in said shell so said side wall of said unit secured to the side wall thh angular POShiOh 0f the major flXeS 0f Said @1011- of said shell; gated openings in successive chamber-forming units the bottom portion of each chamber-forming unit havafhir the unit nearest the gas-admitting and W311 ing an opening of substantially oval shape, the major fers from the angular Position of the major s f axis of said opening substantially equal in length to The Pracedihg elongated Opening y a predetermined the diameter of said bottom portion and the area of g said opening not less than the greater of the areas of A Sikh-ling (lei/1'66 for attachment t0 the eXhauSt areas of said ports in said shell end walls; pipe of an internal combustion engine comprising: said chambenforming units oriented in aid hell so an outer resilient shell having a side wall and opposite the angular position of the major axes of said oval 611d Walls, 0116 end Wall having a P to admit openings in successive chamber-forming units after hflhst gases and the other end wall having a P t0 the unit nearest the gas-admitting end Wall differs discharge Said and from the angular position of the major axis of the Chamber-forming units of resilient material within said preceding oval opening by a predetermined angle, shell defining chambers of progressively smaller size, whereby rotary motion is imparted to exhaust gases the largest of Said Chambers being adlacfiht Said passing through said device to thereby increase the this-admitting end W311, each Chamber-forming llhl't effective length and silencing quality of said device. P- p With the bottom Portion Thereof 3. A silencing device for attachment to the exhaust Stithtihg aphrtlfioh Separating adjacent Chambers and ipe of an internal combustion engine comprising; 60 the side wall thereof constituting a spacer determinan outer resilient shell having a side wall and opposite s the aXial lihglh 0f the Chamber foimed y Said end walls, one end wall havin a port t d it unit, said side wall of said unit engaging the side wall haust gases and the other end wall having a port to of said shell, the bottom portion of each chamberdischarge said gases; forming unit having an elongated opening, the major chamber-forming units of resilient material within said axis of said Opening Substantially equal hi length t0 shell defining chambers of progressively smaller size, [116 diameter of said bottom 130M011 and the a f the largest of aid ha b b i dj i said opening not less than the greater of the areas of gas-admitting end wall, each chamber-forming unit Said Ports in Said Shell and Wallscup-shaped with th b tt ti th f h 9. A silencing device for attachment to the exhaust stituting a partition separating adjacent chambers and P p of all internal Chmbusfion engine comprising! the side wall thereof o tit ti a spacer d i an outer resilient shell having a side wall and at least ing the axial length of the chamber formed by said one and Wall having aP0rt therfiih; and unit, said side wall of said unit engaging the ide chamber-forming units of resilient material within said wall of said shell; shell defining chambers of progressively smaller size,

the, bottom portion of each chamber-forming unit haveach chamber-forming unit cup-shaped with the bottom portion thereof constituting a partition sepa- 1,769,778 7/30 Field 55-419 rating adjacent chambers and the side Wall thereof 1,769,778 7/30 Field 5519 constituting a spacer determining the axial length 1,874,326 8/32 Mason 181-47 of the chamber formed by said unit, said side wall 1,990,837 2/35 Morgenstern 18161 X of said unit secured to the side Wall of said shell, the r, 2,238,316 4/41 M i t 181 59 bottom portion of each chamber-forming unit having 2 77 3 0 3/59 H fif 181 5Q an elongated opening, the major axis of said opening substantially equal in length to the diameter of said FOREIGN PATENTS bottom portion and the area of said opening not less 116,283 2/30 Austrizh than the area Oi. said port in said shell end wall. 10 1,116,944 2/56 France References Cited by the Examiner 303,895 2/59 Great Br UNITED STATES PATENTS 470,904 4/52 1,274,943 8/18 Schmidt 18156 LEO SMILOW, Primary Examiner.

Claims (1)

1. A SILENCING DEVICE FOR ATTACHMENT TO THE EXHAUST PIPE OF AN INTERNAL COMBUSTION ENGINE COMPRISING: AN OUTER RESILIENT SHELL OF SUBSTANTIALLY UNIFORM CROSS SECTION HAVING A SIDE WALL AND END WALLS, ONE END WALL PORTED AND ADAPTED FOR CONNECTION TO THE EXHAUST PIPE AFORESAID, THE OTHER END WALL PORTED AND ADAPTED FOR THE CONNECTION OF A TAIL PIPE FOR EGRESS OF EXHAUST GASES, THE SHELL FABRICATED IN TWO PARTS TO FACILITATE ASSEMBLY, SAID TWO PARTS HAVING OPEN ENDS ADAPTED TO BE JOINED AFTER ASSEMBLY, TRANSVERSE PARTITIONS WITHIN THE SHELL TO DEFINE CHAMBERS OF UNEQUAL SIZE THE LARGEST SAID CHAMBER BEING THAT ADJACENT THE END WALL PORTED FOR THE EXHAUST PIPE AS AFORESAID, AN OPENING IN EACH SAID PARTITION, EACH SAID OPENING HAVING AN AREA NOT LESS THAN THE GREATER OF THE INTERNAL DIAMETERS OF THE SAID EXHAUST AND TAIL PIPES, THE SAID OPENINGS ALIGNED WITH ONE ANOTHER AND WITH THE END WALL PORTS, CYLINDRICAL SPACERS, OF RESILIENT MATERIAL SIMILAR TO THAT OF THE OUTER RESILIENT SHELL, FOR INSERTION WITHIN THE OUTER RESILIENT SHELL, THE OUTSIDE DIAMETERS OF SAID SPACERS EQUAL TO THE INSIDE DIAMETER OF THE OUTER SHELL, THE AXIAL LENGTH OF THE SPACERS SUCH AS TO DEFINE THE DISTANCE BETWEEN SAID TRANSVERSE PARTITIONS, THE OUTER RESILIENT SHELL AND THE RESILIENT SPACERS AFORESAID COMPRISING A COMPOSITE SHELL OF TOTAL THICKNESS NOT LESS THAN THREE SIXTEENTHS OF AN INCH.

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