US3688869A

US3688869A - Muffler with resilient exterior

Info

Publication number: US3688869A
Application number: US160033A
Authority: US
Inventors: Milo E Murphy
Original assignee: MURPHY MUFFLERS
Current assignee: MURPHY MUFFLERS
Priority date: 1971-07-06
Filing date: 1971-07-06
Publication date: 1972-09-05
Anticipated expiration: 1989-09-05
Also published as: CA971844A

Abstract

A muffler for high velocity gases has intake and exit ports at the ends of a container. The container is defined by a flexible or resilient sheath forming exterior walls between the ports. A frame of metal or other rigid material supports the sheath and baffles divide the container volume. An edge of each baffle is in contact with the inner surface of the sheath. Gas passes from one divided volume to another across the baffle edges, displacing the sheath at that area and losing energy. Each frame has attachments to secure the container to the source or consumer of the gas.

Description

United States Patent Murphy Sept. 5, 1972 [54] MUFFLER WITH RESILIENT [56] References Cited EXTERIOR UNITED STATES PATENTS [721 Murphy 1mg Beach Cahf- 3,225,861 12/1965 Reynolds ..1s1/4'/ A [73] Assignee; Murphy Mufflers, L05 Ang le 3,482,649 12/1969 Murphy ..l8l/47 A Calif. Primary ExaminerRobert S. Ward, Jr. [22] Flled: July 1971 Attorney.lacquet Gribble [2]] Appl. No.: 160,033

ABSTRACT Related Apphumon Data A muffler for high velocity gases has intake and exit [63] Continuation-impart of Ser. No. 25,438, April ports at the ends of a container. The container is 3, 1970, Pat. No. 3,590,945. defined by a flexible or resilient sheath forming exterior walls between the ports. A frame of metal or other [52] US. Cl ..l8l/40, 181/47 A, 181/64 A, rigid material supports the sheath and baffles divide 181/65 the container volume. An edge of each baffle is in 511 1111. (:1. ..F01n 1/08,F01n 1/22, FOIn 7/10 Contact with the inner surface of the sheath Gas [53] Fi of Search 131 3 40 47 47 A 5 4 R, passes from one divided volume to another across the baffle edges, displacing the sheath at that area and losing energy. Each frame has attachments to secure the container to the source or consumer of the gas.

19 Chins, 16 Drawing Figures f9, 4 f3 2/ a 4/ 5;

pet I u 2;

, '2 4 2 (7 i I -Z PATENIEBstr sum 3.888.889

sum 1 at 4 mwwqtany i MUFFLER WITH RESILIENT EXTERIOR This application is a continuation-in-part of my copending application, Ser. No. 25,438 filed Apr. 3, 1970, entitled Tuned Resonance Muffler," now US. Pat. No. 3,590,945.

BACKGROUND OF THE INVENTION The invention relates to mufflers for gas intake and exhaust systems and more particularly to such systems where gas velocity is high.

With population density increasing in every area and a like increase in the use of power equipment, noise emissions have reached a level hazardous to physical and mental health. Attempts to muffle the noise output of gas and air consuming and gas-emitting devices such as vehicles, hobby engines, air motors and brakes have been defeated because of cost for such mufflers or the depressing of power output of the device because of the muffler. The present invention is not only low in cost but can be tuned to increase engine efficiency as well as to damp sound output, particularly in the high frequencies which are injurious and annoying.

In my copending application a muffler with a resilient sheath of silicone rubber or Neoprene rubber was disclosed. Satisfactory performance has resulted with the invention set forth therein. However, it has been discovered that improved performance and longer life can be achieved in such mufflers by use of uniquely reinforced sheath materials in which the sheath is a laminate of heat resistance materials, one of which is a stretch" fabric.

SUMMARY OF THE INVENTION The invention contemplates a muffler for high velocity gas which comprises a gas impervious sheath supported on a frame to define a container. The frame has members in contact with the surface of the sheath to close the container. The sheath is elastic or flexible to be displaced from the member edges by the gas pressure to pass gas across the member edges out of the container. The sheath may be made of silicone or Neoprene" rubbers laminated with stretch fabrics such as Spandex" or knitted Dacron.

Preferably the container has a plurality of chambers defined by frame members such that the gas energy is successively lowered by the successive lifting of the elastic sheath away from the member edges to create intermittent gas passages from one chamber to another and to emerge from the container.

The muffler of the invention has equal usefulness for quieting the passage of intake gases such as air as it has for exhaust gases or air from power tools and internal combustion engines. These and other advantages of the invention are apparent from the following detailed description and drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a plan view of a hobby engine muffler in accordance with the invention;

FIG. 2 is a fragmentary sectional elevation taken along line 2-2 of FIG. 1;

FIG. 3 is a transverse sectional view taken along line 3-3 of FIG. 2;

FIG. 4 is a fragmentary sectional view of an alternate embodiment of the invention having a laminar sheath;

FIG. 5 is a fragmentary sectional view of a further alternate embodiment with a differing laminar sheath;

FIG. 6 is a plan view of a further alternate embodiment of the muffler of the invention adapted to small hobby engines;

FIG. 7 is a fragmentary sectional elevation taken along line 7--7 of FIG. 6;

FIG. 8 is an elevational view, partly in section, of an air tool combined with a muffler of the invention;

FIG. 9 is a fragmentary elevation, partly in section, of

an air tool combined with an alternate embodiment of the invention;

FIG. 10 is a fragmentary transverse section taken along line 10l0 of FIG. 9;

FIG. 11 is a perspective view, partly in section, of an alternate embodiment of the invention adapted to use with heavy vehicle exhaust systems;

FIG. 12 is a plan section, partly broken away, taken along line l2l2 of FIG. 11;

FIG. 13 is a side elevation, partly in section, of a further alternate embodiment for use with heavy vehicles;

FIG. 14 is an end elevation, partly in secton, of the embodiment of FIG. 13;

FIG. 15 is a side elevation, partly in section, of a still further alternate embodiment of the invention for heavy exhaust systems; and

FIG. I6 is a longitudinal section of an embodiment of the invention suited to gas or air intake muflling.

In the various views like parts are referred to by like reference numerals.

The sheath of the invention is referred to variously as resilient or flexible" or "elastic." Each of these qualities is desirable in the material from which the sheath is made. The sheath is so defined to describe its qualities of recovery from deformation due to the gas pressures to which it is exposed. Materials such as Dow-Cornings silicon rubber are exemplary of the materials intended. That companys Silastic 55" has performed well in tests on various types of installations.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIGS. 1-3 a muffler 21 adapted for use on small hobby engines is shown. The muffler comprises a metallic tube 22 having side walls 23, 24 and top and bottom walls 25, 26, respectively, which define a volume 28 which is open at edge 29 for attachment to a source of gas, such as a 0.049 cubic inch model airplane engine (not shown). Opposed pegs 31, 32 afford mounts for a tension spring (not shown) which encircles the motor and holds the muffler 21 in position at the exhaust port of the motor. This arrangement is disclosed in the aforesaid copending application.

The top and bottom walls 25, 26 have a plurality of parallel fins 34 extending across their outer surfaces. Interiorly of the walls 2326 are a plurality of baffles, such as the baffles 37, 38 of FIG. 3, which are spaced transversely between the walls 23, 24 and extend in the direction of gas flow from entry end 29 of the muffler.

A sheath support frame is integrally formed with the walls 23, 24. The frame comprises side members such as the members 41 of FIGS. 2 and 3 and an end member 42 extending between the spaced side members 41. The frame members support a tubular gas impervious sheath 44 which has top and bottom walls 45, 46 and

side walls

47, 48. The top and bottom walls extend between the frame members 41 of the sheath support. Preferably the sheath is sealed to the tube by an adhesive layer 51, as shown in FIG. 2.

An intermediate frame member baffle 53 extends between the side walls 41. Both the end frame member 42 and the frame member baffle 53 have edge surfaces 55 in contact with the interior of the sheath. Gas entering the muffler traverses the baffles 37, 38, losing heat to the baffles which is radiated through the fins 34. The gas then enters the container defined by the sheath and forces a sine wave undulation of the sheath, periodically moving the sheath from the contact surfaces 55 of the baffle 53 and the frame end member 42 such that gas exhausts around the baffle and the frame member to atmosphere.

The muffler 21 of HO. 1 may be tuned with respect to resonance by manipulation of a transverse sliding valve plate 61 secured to frame member baffle 53 on its downstream face. The downstream location of the valve plate is for convenience only since a screw driver can be inserted to the valve plate from the entry end 29 of the muffler.

The valve plate has a circular port 62 and an elongate slot 63 through which a slotted screw 64 extends into threaded engagement with frame member baffle 53. Baffle 53 has a port 65 centrally thereof. By manipulating valve plate 61 to cover more or less of the port 65 the direct interchange of exhaust gas into a second chamber 67 of the container may be regulated in accordance with the basic resonance of the exhaust.

It has been found that the effectiveness of the muffler may be increased by a laminar sheath. Therefore the sheath 44 of the embodiment of FIG. 1 has a cloth laminate 68 adhered to both the top and bottom walls of the sheath. The laminate is preferably a synthetic cloth material, like Dacron, woven to have stretch in one direction. By arranging the laminate such that its direction of stretch coincides or deviates from the flow axis of the muffler, the sine wave action of the sheath may be varied in accordance with the desired resonance frequency.

FIG. 4 is a fragmentary transverse section of an alternate embodiment of the invention wherein the laminar construction of the sheath 44A varies from that shown in the embodiment of FIG. 1. The muffler may be similar to the muffler 21 and the sheath be supported on frame members like member 41 and have a central frame member baffle 53. The sheath, which is basically of a silicone rubber, such as that made by Dow-Corning, or of a heat resistant Neoprene, has first and second laminates bonded to the top 45 and the bottom 46 of the sheath. A first stretch fabric laminate 71 is bonded by a suitable adhesive 72 to the outer surface of the sheath. A foamed silicone rubber is used for the second exterior laminate 74 on each of the top and bottom of the sheath. Preferably the fabric is a woven Dacron with a one-way stretch weave, such as Mohawk Mills fabric D117 knit.

It is believed that the series of laminates, including the basic silicone rubber of the sheath, act in like manner to radio waves with respect to reflection and absorption at the interface between layers. The second waves are believed to be reflected or absorbed in the harmonics of the basic resonance of the wave. One reflection is a half harmonic of the basic cyclical rate of the wave. Another reflection is a multiple of the frequency of the wave. Thus, a 2,000-cycle wave is believed to be reflected in a LOGO-cycle component and a 4,000-cycle component, while the basic 2,000-cycle component penetrates to the next layer. Each succeeding interface would thus raise the frequency of the basic wave. The resilient or flexible muffler sheath has suppression characteristics which make it more efficient in the higher frequencies. Thus, a multiplicity of interfaces increases the efficiency of the muffler.

While Dacron and foam silicone rubber have been mentioned as laminates, various laminates may be used that are heat-resistant, flexible and capable of responding to the convolutions of the basic silicone rubber sheath imposed by the pulsing gas passing through the muffler. Thus, bias-woven Dacrons may be utilized for a two way stretch effect.

The placement of the laminates, and thus the placement of the interfaces, affects the magnitude of the sine wave fluctuation of the sheath. Magnitude is inhibited inwardly by inward lamination and inhibited outwardly by an outward lamination. It should be understood that the application of radio wave theory to the sound wave absorption pattern of the flexible muffler sheath is speculative. However, tests of laminated sheath mufflers at a motor manufacturing test facility tend to support the theoretical conclusion.

In accordance with this theory, an alternate embodiment of the invention is shown fragmentarily in FIG. 5 in which a muffler 21A has a support frame member 41 which is one of a spaced pair. An intermediate frame member baffle 53 divides the compartment defined by the silicone rubber sheath 44B into chambers. As in the embodiment of FIG. 1, the second chamber is closed by a frame member 42 (not shown). The sheath 44A of FIG. 5 has an inner laminate which may be of a stretch Dacron material. The inner laminate 77 is midway between the inner and outer surfaces of the sheath and extends through the sheath such that the sheath and the laminate may be extruded as a tubular length. The sheath may then be cut into segments of proper length to fit the particular muffler.

By virtue of its intermediate position in the thickness of the silicone rubber of the sheath, the inhibiting effect of the fabric layer is balanced between the inner and outer fluctuations of the sheath. Fluctuation of the silicone sheath is maximized in a laminar construction when the fabric is applied in bias fashion, giving a twoway stretch effect. Back pressure may be reduced by reducing or damping the sine wave fluctuation of the sheath, in which case the fabric is united with the sheath material such that the stretch of the fabric is transverse the direction of gas flow. it has been found that minimizing the magnitude of sine wave fluctuation generally results in lower back pressure imposed by the muffler on the exhaust stream.

Another fabric which has proved to be useful as a laminate with the muffler of the invention is sold under the trade name Nomex. This material is a high-temperature knitted nylon with stretch capabilities in two directions.

FIGS. 6 an 7 illustrate a muffler in accordance with the invention adapted for use with small hobby engines in the range of 0.010 to 0.15 cubic-inch displacement. The particular proportions shown in FIGS. 6 and 7 are for the 0.049 cubic-inch displacement engine.

The engine is fragmentarily shown, the fuel tank 81 being to the left of FIG. 6 and the propeller shaft housing being shown at 82 broken away. FIG. 7 shows the cylinder 83 and an exhaust port 84 and a second exhaust port 85. A rectangular gas-impervious sheath 87 surrounds first and second shells 88, 89 which comprise the sheath support frame. Each shell has an upper wall 91 and a lower wall 92. The inner surface 93 of each wall is arcuate to mate with the outer surface of the cylinder. Each shell is oriented to encompass an exhaust port. Each shell has opposed side walls, such as the wall 94, shown in FIG. 7. The shell thereby defines a tube having a rectangular opening at one end and an arcuate opening at the other.

The sheath 87 surrounds the shells, closing the open rectangular ends to define a container on each side of the cylinder and retaining the shells on the engine. Gas exhausting from the

ports

84, 85 enters the container defined by the sheath and fluctuates the sheath away from the contact surfaces 96 of the shell walls to create a fluctuating gas passage for exhausting gas. The gas must displace the sheath in order to escape the container and, in deforming the sheath, loses energy in addition to the energy lost through heat transfer to the metallic shell.

Noise suppression is also aided by the fact that there is a time lag between the engine explosion and the time that the gas pressure displaces the sheath from the contact surfaces.

Like the previously described embodiments, the sheath may be of a silicone rubber or a Neoprene and may be laminated with a fabric, so long as the elasticity of the sheath is not inhibited to the extent that the shells cannot be assembled about the cylinder.

In FIG. 8 a hand-held air tool 101, such as that made by Aero Tool Company, is shown fragmentarily. The air tool comprises an inlet cylinder 102 having a snap fitting 102A for quick coupling of air hoses, an intermediate reduced diameter cylinder 103, and a tool holding member 104. Conventionally, a threaded connection exists between

portions

102 and 103. The particular mechanical arrangement of the air tool varies from manufacturer to manufacturer and some tools may not have a reduced portion 103. Therefore, the muffler 105 of FIG. 8 has a sheath support frame 106 which comprises a first arcuate member 108 and a second arcuate member 109. Each member has a 180 wall 111 spaced from a like wall 112. The walls are joined in each member by a cylindrical half drum 114. The drum divides the member into an inner chamber 116 and an outer chamber 117. The inner surface are 119 of each wall seats upon the periphery of tool cylindrical section 103. A plurality of ports 121 connects the volumes of chambers 116 and 1 17 in each member.

Conventionally, the reduced portion 103 of the air tool has a plurality of exhaust ports 124. The air exhausting from the motivating piston of the tool enters the inner chamber 116 and passes out through the ports 121 into the outer chamber. The air may be guided within the inner chamber by a spiral spring 126 whose basic function is to provide proper spacing of the drum from the periphery of portion 103.

Preferably the outer chamber is divided by annular ribs 127 into compartments. The ribs are frame members which have contact edges 128 in contact with the inner surface of a cylindrical sheath 129. The sheath may have a flange 131 at one end which parallels the wall 1 12 of the sheath support frame 106.

Like the previous embodiments, gas exhausted from the ports 124 enters a first compartment 133 which is defined between the sheath and the sheath support frame and the gas pressure displaces the sheath outwardly away from the contact surface 128 of the rib adjacent the connecting port 121. The gas then passes into a second compartment 134 and thence to the third compartment 135 and outwardly over the contact edge 137 of wall 111 to atmosphere.

Unlike the support frame, the sheath 129 of the embodiment of FIG. 8 is a continuing annulus and through its elasticity maintains the separated support frame members in place upon the air tool. In this fashion the sheath of the embodiment of FIG. 8 coacts with the support member in like manner to the sheath of the embodiment of FIG. 6.

FIGS. 9 and 10 illustrate a further alternate embodiment of the invention wherein a muffler 141 is attached to an air tool 142 similar to the tool 101 of FIG. 8. The muffler has a cylindrical sheath 144 with an inward flange 145 integrally formed therewith. The sheath may be of silicone rubber and may be fabric laminated as in the embodiments of FIGS. 4 and 5. However, satisfactory operation has been experienced without a laminate structure of the sheath in the particular use illustrated by FIG. 9. A support frame 146 holds the sheath in place on the air tool. The support frame comprises spaced

annular side members

147, 148 which circumscribe the reduced cylindrical portion 103 of the air tool. Portion 102 is conventionally removable so that the unitary support member may be placed on a reduced diameter portion.

A drum 151 divides the container 152 defined by the sheath and frame members into an inner chamber 153 and an outer chamber 154. A plurality of ports, like the port 155, communicates between the inner and outer chambers.

The outer chamber 154 is further divided by a circumferential rib 156. The circumferential rib has a contact surface 157 in contact with the sheath. Each of the

frame members

147, 148 has a like contact surface 158 in contact with the sheath such that the sheath closes the outer compartment.

As can be seen from FIG. 10, in which circum ferential rib 156 is shown fragmentarily, a plurality of transverse baffles 161 divide each compartment 159, 160 of the outer chamber into smaller chambers. Each baffle 161 has a contact surface 163 which contacts the sheath 144.

A clamp ring 165 seals the inner surface of the sheath against the contact surface 158 of frame member 148. Escape of gas from compartment 160 across surface 158 is thus obviated. The band may be of various tension clamping types or may be a ring, such as that used for automobile radiator hoses.

The operation of the embodiment of FIG. 9 is similar to that of the embodiment of FIG. 8 in which air exhausting through tool ports 124 communicates through port 155 into the chamber 154 such that the sheath is deformed to create a gas passage across contact surface 156 into compartment 159 and thence out across surface 158 to atmosphere.

FIGS. 11 and 12 illustrate schematically a further alternate embodiment of the invention for use with heavy duty vehicles, such as diesel trucks, and with other internal combustion engines. In the Figures a muffler 171 in accordance with the invention has an outer sheath 172 made up of four

rectangular portions

173, 174, 175, 176 which define a muffler container. Each of the portions is supported by a support frame comprised of inner and outer

vertical angles

178, 179 at each corner and top and bottom pans 181, 182, respectively. Each sheath portion is sealed to the pans in convenient fashion. A flanged intake duct 183 passes through the bottom pan opening into a chamber defined by the sheath and a horizontal divider 185. The divider 185 is shown fragmentarily in FIG. 12. The chamber is further divided into four compartments of which two compartments, 187, 188 are small.

Compartments

189, 191 are larger compartments. The compartments are divided by diagonal

vertical walls

193, 194, 195, 196 which converge centrally of the duct 183. Successive

horizontal dividers

197, 198, 199 further subdivide the container defined by the sheath.

Each of the dividers 185 and 197-199 supports verti cal dividers, like the dividers 193-196. Only the top and bottom pans 181, 182 are apertured. The horizontal dividers are not.

Each of the horizontal dividers has an outer contact edge in contact with the adjacent inner sheath surface. Gas from a vehicle or engine exhaust enters duct 183 into the four compartments shown in FIG. 12 and transfers to the concomitant compartments above the next divider by displacing the sheath away from the contact edge and passing across that contact edge. The gas therefore passes in successive stages through the various compartments independently in each of the series of chambers. The gas then passes from the last chambers above divider 199 through a discharge duct 201, which is flanged and attached to the top plan similarly to the lower duct 183.

In use on a diesel truck the intake 183 of the illustrative embodiment of FIG. 11 may be a four-inch [.D. tube adapted to fit over the 3 7/8 I.D. exhaust tube of the conventional diesel exhaust system. Effective muffling of the exhaust gases was achieved in a muffler in which the narrower

end sheath panels

175, 176 were approximately 12 inches in width and the

longer sheath panels

173, 174 were approximately 24 inches in width. The sheath had a vertical dimension of approximately 24 inches with the dividers being approximately four inches apart vertically. Tests conducted by the California Highway Patrol Test Unit indicate that a sheath of silicone rubber of it: inch wall thickness is an effective sheath material for use with heavy vehicles. The tests involved a muffler in accordance with the invention with a lesser number of dividers than the embodiment of FIG. 11. Decibel reductions in a ranged of 50 per cent were achieved by the test muffler.

While angle iron support members have been shown, it is within the contemplation of the invention to utilize other framing members to so anchor the sheath such that under conditions of no gas flow there is intimate contact between the horizontal divider edges and the inner surface of the sheath.

The alternate embodiment of FIG. 11 is particularly effective to muffle the noises of engines wherein the the vehicles are equipped with compression braking systems, such as the Jacobsen brake system. Because the sheath is of an elastic material, the displacement gap between the sheath and the divider edge varies with the gas pressure and volume such that the muffler adapts to a great fluctuation in exhaust volume. The muffler is therefore effective in combatting the awesome pulsations resulting in the muffler system from the operation of the J acobsen brake.

The alternate embodiment of FIGS. 13 and 14 illustrate a muffler in accordance with the invention having a greater capacity than the muffler of FIG. 11. In the Figures a muffler 211 utilizes a plurality of discontinuous sheaths to define a plurality of containers receiving high velocity gas from a common manifold. As can be seen from FIGS. 13 and 14 an attachment duct 212 which may be 4-inch l.D. pipe feeds into a rectangular manifold 214 which is preferably of a metallic material. Other substances of equal strength may be substituted for the metal of the manifold. Four sheathed containers 215-218 are shown in FIG. 13. The number of muffler containers may vary with the desired capacity of the muffler. Each of the containers is similar in structure such that a description of one will suffice for all. As can be seen from FIG. 13, container 218 is supported upon a manifold pan 221. The container has sheath panels 222, 223 extending between end pieces like the

support frame members

224, 225 of FIG. 14. Top and

bottom support stringers

227, 228 connect between the end frame members. The container defined by the support frame and the sheath, which, while discontinuous in the illustrative embodiment, may be a continuous tube, is further divider by

horizontal dividers

231, 232 which are supported from the

end frame members

224, 225. An inner frame member 234 has a port 235 connecting with a pan port 236 which opens into the manifold. The ports may be elongate or may be a plurality of separate aligned apertures in the pan and in the support member.

Each sheath is secured to the support frame by exterior stringers at each end. The stringers 241, 242 of FIG. 14 are exemplary.

Horizontal dividers

231, 232 have side edges in contact with the sheath. A sheath stretched to high tension between the

side members

224, 225 can remain in contact with the edges. However, it is desirable to insure contact of the sheath and the dividers and top stringer 227 in incremental segments of contact. Therefore, a plurality of exterior straps 251 is anchored vertically across each sheath component to insure surface contact between the sheath and the divider edges. The sine wave fluctuation of the sheath is thus inhibited, resulting in a lower back pressure. The straps thus function as a discontinuous laminate exteriorly of the sheath to effect fluctuation damping in the same manner as the laminated fabrics of the embodiments of FIGS. 4 and 5.

In operation, the embodiment of FIG. 13 is similar to the previously described embodiments, accepting high velocity gas at intake duct 212 and discharging the gas in the momentary apertures between sheath and dividers resulting from the fluctuations of the sheath with respect to the dividers. The fluctuations vary with the pressure and volume of the gas to which the muffler is exposed.

The sheath again may be of silicone rubber or Neoprene and, in addition to the laminar straps 251, may be comprised of fabric and silicone rubber laminations, as in the previously described embodiments.

A further alternate embodiment is shown schematically in FIG. in which a muffler 261 in accordance with the invention has means for attachment to a source of exhaust gas, such as a heavy vehicle, comprises of an inlet tube 262 and a cruciform manifold 263. The manifold is roofed by a pan 266 having peripheral downturncd flanges 267 Each of four exterior muffler sheath panels 269 is sealed at its bottom to each of the four flanges 267 of the pan. Corner angles 271 are anchored through the sheath to the pan flange at each corner. A downwardly oriented channel 273 extends across each side of the muffler. The channels 273 are mitered at each corner and joined together to define a hollow square. The top of each outer sheath 269 is fixed at each corner to the flange 274 of each upper channel 276 as is the angle 271. Each of four inner sheath panels 276 is secured by a corner angles 277 at each inner corner of the hollow square. Each inner sheath is secured at its bottom to one of four bottom anchor angles 278 which seat upon the pan and define a hollow square at the bottom of the muffler where it joins the manifold pan. The angles 277 are also secured to each of the four anchor angles 278. The structure thus described defines a muffler compartment in the configuration of a hollow square. Each of the eight vertical side of the square is sheathed by either an inner sheath 276 or an outer sheath 269. Gas enters intake duct 262 and is distributed through the arms of the crucifix manifold into each of the sides of the square through ports in the manifold pan like port 281.

The muffler container is divided into chambers by

horizontal dividers

283, 284, 285. Each of the horizontal dividers may be a sallow channel and the dividers of one container compartment may be joined at their corners such that the chambers are continuous around the hollow square. Although such a configuration is desirable, the invention does not preclude a division at each corner between the compartments of each portion of the square. However, it is desirable to have one of the horizontal dividers movable to effect resonance tuning of the muffler. The moving mechanism is simplified if the four horizontal dividers at a particular vertical level are unitized. As seen in FIG. 15, the upper divider 285 is coupled to a threaded crank 291 which is threadably engaged with a nut 292 fixed to frame end member 273. The lower end 293 of the crank is free to turn within the divider 285 and is secured thereto by C-rings 286. Two or more cranks may be used in each portion of opposite sides of the square such that the divider may be displaced equally along a vertical line.

While the illustrative embodiment of FIG. 15 shows apparatus for moving the upper horizontal divider, the invention does not preclude extension of the crank end 293 to be affixed to any of the lower horizontal dividers to achieve tuned resonance by vertical displacement of any of the dividers.

As described with respect to the previous embodiment, that of FIG. 13, discontinuous laminates may be applied to both the exterior and interior sheath portions to insure incremental contact between the contact edges of both the horizontal dividers and the top member 273 and the internal surface of the sheath. Preservation of the contact between the sheath and the horizontal dividers insures energy absorption from the moving gas column as it must displace the sheath to create a passage about the dividers to exhaust to atmosphere.

The embodiment of FIG. 15 is thus adapted to use on heavy engines and vehicles using air compression braking systems. The muffler may be tuned to the optimum resonance of the muffler system to which it is attached and achieves a much lower sound output than conventional muffler systems.

While the illustrative embodiment of the FIG. 15 is applicable to attachment to existing muffler systems, an adapter may be used with duct 262 to attach the muffler directly to the exhaust manifold of an engine. Equal noise reduction results from such attachment.

In FIG. 16 an embodiment of the invention adapted for use at a gas intake is illustrated. Vehicles such as snowmobiles and most vehicles equipped with internal combustion engines emit harmful and unpleasant sound at the carburetor or other air intakes. In the embodiment of FIG. 16 a muffler container 301 is comprised of a tubular silicone rubber sheath 302 supported on a frame 303 having a plurality of

transverse baffles

304, 305, 306 upstream of an end frame member 307. Baffle 305 is longitudinally articulate by means of a screw 311 threaded in end baffle 304. The muffler can thereby be resonance-tuned.

A screwtab 308 on the downstream end of the container 301 affords means for securing the container to a shell 309. Suitable fastening means anchor the tab to the wall of the shell. An entry port 312 in the upstream end of the shell connects to the container. Unturned lip 313 on the shell at the port receives the end of the sheath 302. The sheath is suitably sealed to the lip as by adhesive, tension band or clamp.

The shell may be of any rigid material such as aluminum or Cycolac plastic. The shell is larger than the muffler container such that a gas envelope 314 intervenes between the two. The shell is necked down to an exit port 315 which leaves an interval between the shell and the container. Pegs 316 afford attachment for a tension spring 317 which encircles the air using device the muffler serves.

In operation, air enters the container at 312, fluctuates the sheath into the gas envelope 314 as air traverses the periodic intervals between the bafile edges and the sheath. The suction at 215 induces the air flow through the container and maintains a less than atmospheric pressure in the surrounding envelope 314.

Each of the illustrative embodiments described above affords efficient, effective suppression of noise from high velocity gas movement, whether the gas is incoming or exhausting. The laminar sheath affords a muffler of long life and controllable fluctuation magnitude. The mufflers may be tuned as to resonance for increased efficiency of the attached device.

Many modifications within the scope of the invention other than those disclosed herein will occur to those skilled in this art. Therefore, it is desired that the invention be measured by the appended claims rather than by the illustrative embodiments described.

I claim:

l. A muffler for attachment to a high velocity gas device comprising a gas impervious sheath defining a container, a frame supporting the sheath, frame members, edge surfaces on the frame members adapted to contact the sheath to close the container; attachment means on the frame, and gas entry means on the frame; said sheath being of a resilient material adapted to be displaced from the frame member edges under gas pressure to pass gas from the container defined by the sheath.

2. A muffler in accordance with claim 1 further comprising a plurality of frame members dividing the container into compartments, a contact edge on each member adapted to contact the sheath.

3. Apparatus in accordance with claim 1 wherein the sheath also comprises the attachment means.

4. Apparatus in accordance with claim 1 wherein the frame comprises first and second shells, each having walls defining a chamber open at both ends, an entry end of each shell being adapted to seal to the source of gas, and the other end of each shell being closed by the sheath, said sheath encircling both shells and restricting the entry end of both shells against the high velocity gas device.

5. Apparatus in accordance with claim 4 wherein the walls defining the chamber are arcuate.

6. Apparatus in accordance with claim 5 further comprising a plurality of frame members dividing the chamber into a plurality of compartments, and a contact edge on each frame member adapted to contact the sheath.

7. Apparatus in accordance with claim 1 wherein the frame comprises spaced annular side walls, a drum extending from wall to wall intermediate of the depth thereof to define an inner entry chamber and an outer chamber; a port in the drum communicating between chambers, a plurality of frame members dividing the outer chamber into compartments, and a contact edge on each frame member adapted to contact the sheath to close the compartment.

8. A muffler in accordance with claim 1 wherein the frame comprises top and bottom pans, corner members connecting between pans, and the sheath comprises a plurality of panels each sealed to the frame at all but one panel side.

9. A muffler in accordance with claim 8 further comprising at least one baffle member intermediate the pans.

10. A muffler in accordance with claim 9 wherein the attachment means comprises a tube and a manifold connecting to the tube, said manifold opening to the container.

11. A muffler in accordance with claim 9 wherein the frame further comprises inner corner members connecting between pans, said pans defining a hollow square volume, and the sheath further comprises a second plurality of sheath panels extending between the top and bottom pans, each panel being sealed to the frame at all but one panel side.

12. A muffler in accordance with claim 9 further comprising means for changing the intermediate position of a baffle member with respect to the pans.

13. A muffler in accordance with claim 1 wherein the sheath comprises a laminated material capable of flexiilifiifrlfli'l'? ifi ffil'lill llim 13 wherein the laminate material comprises an inner laminate of silicone rubber and an outer laminate of foamed silicone rubber.

15. A muffler in accordance with claim 13 wherein the laminated material comprises one laminate of silicone rubber and one laminate of a synthetic knit fabric having stretch capability in at least one direction.

16. A muffler in accordance with claim 15 wherein the laminated material further comprises a laminate of foamed silicone rubber.

17. A mufi'ler in accordance with claim 15 wherein the direction of fabric stretch is parallel to the path of gas through the muffler.

18. A muffler in accordance with claim 15 wherein the direction of fabric stretch is at an angle to the path of gas flow.

19. A muffler in accordance with claim 1 further comprising a shell surrounding the container, means sealing the shell to the container at the entry end thereof such that gas enters the container only, and means connecting both the shell and the container to the high velocity gas device for gas interchange therewith.

* It i i

Claims

1. A muffler for attachment to a high velocity gas device comprising a gas impervious sheath defining a container, a frame supporting the sheath, frame members, edge surfaces on the frame members adapted to contact the sheath to close the container; attachment means on the frame, and gas entry means on the frame; said sheath being of a resilient material adapted to be displaced from the frame member edges under gas pressure to pass gas from the container defined by the sheath.

13. A muffler in accordance with claim 1 wherein the sheath comprises a laminated material capable of flexing and restoration to unflexed condition.

14. A muffler in accordance with claim 13 wherein the laminate material comprises an inner laminate of silicone rubber and an outer laminate of foamed silicone rubber.

17. A muffler in accordance with claim 15 wherein the direction of fabric stretch is parallel to the path of gas through the muffler.