Catalytic muffler and method

Abstract: A catalytic muffler (10) includes a housing having an inlet (14), an outlet (16), and a plurality of catalyst coated serially stacked perforated cups (18,20,22) through which exhaust flows and is acoustically attenuated and catalyzed.

Description: The invention relates to catalytic mufflers. Catalytic mufflers are known in the art, and perform both a noise baffling muffling function and a catalytic function. One catalytic muffler known in the art (EP 0 530 493 A2) comprises a plurality of elements made of porous ceramic material treated with catalytic material for depleting the exhaust-gas of the pollutants. Those elements - diaphragms - are tagged end to end within a tube. The diaphragms are prepared with different perforated surfaces in order to allow the exhaust-gases to pass through the diaphragms. The main advantage of the above muffler is the fact that different mufflers may be assembled out of a limited quantity of components. However, this flexibility concerning customisation and performance is rather restricted. Another technical solution concerns a silencer for a compressed air installation (EP 0 127 550 A2). The silencer is having an inlet and an outlet and a plurality of cylindrical baffles. Each baffle is perforated along a perforation pattern. Air flowing through one baffle and through its perforation pattern is redirected as to be able to flow through the perforation pattern of an adjacent baffle. This leads to an improved performance in terms of reducing the resulting noise of the airflow. This particular prior art is to be considered technological background to the present invention. The present invention provides a simple and effective catalytic muffler system which may be readily adapted to varying muffling and catalyzing requirements. Acoustic and catalytic properties may be readily varied, including increased baffling of noise and exhaust to surface area time, as well as optimization of catalyst formulation. Customisation to particular application needs as well as increased performance are readily accommodated. The invention is defined in claim 1. Preferred and advantageous versions of the invention are the subject of the sub-claims. Hereafter the invention is described with reference to the drawings illustrating preferred embodiments. In the drawings Fig. 1 is a schematic exploded perspective view illustrating construction of a catalytic muffler in accordance with the invention, Fig. 2 is a schematic side sectional view of the assembly of Fig. 1 in a housing, Fig. 3 is an end view of a component of Fig. 1 and shows an alternate embodiment. Figs. 1 and 2 show a catalytic muffler 10 including a housing 12 having an inlet 14, an outlet 16, and a plurality of catalyst-coated perforated cups 18, 20, 22 between inlet 14 and outlet 16. Exhaust flowing through housing 12 from inlet 14 to outlet 16 is acoustically attenuated and catalyzed by the perforated cups 18, 20, 22. The cups are stacked as shown at arrows 24, 26, 28 in serial relation such that exhaust flows serially through the cups, namely through first cup 18, then through second cup 20, then through third cup 22, and so on if additional cups are used. Each cup 18, 20, 22 has an open end 30, 32, 34, respectively, a closed end 36, 38, 40, respectively, and a closed-loop, preferably annular, sidewall 42, 44, 46, respectively, between the respective open end and the respective closed end. Each cup is perforated along a respective perforation pattern 48, 50, 52 through at least one of the respective closed end and respective sidewall. Fig. 1 shows perforation patterns through the sidewalls. Fig. 3 shows a perforation pattern 54 through end wall 40, which end wall perforation pattern may be provided through one or more of the remaining cups instead of or in addition to the perforation pattern through the sidewall. Cups 18, 20, 22 are stacked in nested relation with closed ends 36, 38, 40 adjacent each other, sidewalls 42, 44, 46 adjacent each other in concentric relation, and open ends 30, 32, 34 adjacent each other. Support structure, to be described, provides a gap between at least one of: (a) closed ends 36, 38, 40; and (b) sidewalls 42, 44, 46. In preferred form, perforation patterns of adjacent cups are non-aligned, to maximize baffling of noise and increase exhaust to surface area time. In the embodiment of Fig. 1, the perforation patterns are through the sidewalls, and the gaps are between the sidewalls of adjacent cups. In the particular embodiment of Fig. 1, first cup 18 is nested into second cup 20 which is nested into third cup 22. Perforation pattern 48 through sidewall 42 of first cup 18 is circumferentially distally opposite perforation pattern 50 through sidewall 44 of second cup 20; and perforation pattern 50 through sidewall 44 of second cup 20 is circumferentially distally opposite perforation pattern 52 through sidewall 46 of third cup 22. In another embodiment, the perforation patterns are through the closed ends, Fig. 3, and the gaps are between the closed ends of adjacent cups. In a further embodiment, perforation patterns are formed through both the sidewalls and the closed ends of the cups, and the gap is formed between both the sidewalls and the closed ends of adjacent cups. In a further embodiment, the muffler includes an air induction duct 54 in housing 12 supplying air to one or more gaps between cups to optimize catalyst formulation. In one embodiment, the noted support structure is provided by lip flanges 56, 58, 60 at respective open ends 30, 32, 34, which lip flanges engage each other in overlapped relation such that the lip flange 56 of a first cup - inner cup - such as 18 engages the lip flange such as 58 of a second cup - outer cup - such as 20 to locate and suspend the inner cup within the outer cup, and such that lip flange 58 engages lip flange 60 of the next outer cup to locate and suspend inner cup 20 within the next outer cup 22, and so on. In another embodiment, raised shoulders such as shown in dashed line at 62, 64 are provided on respective closed ends 36, 38, engaging the closed end of the next cup to locate and space adjacent cups, i.e. raised shoulder 62 engages closed end 38 to locate and space adjacent cups 18 and 20, and raised shoulder 64 engages closed end 40 to locate and space adjacent cups 20 and 22, etc. In another embodiment, the support structure comprises a mounting plate 66 mountingly engaging open ends 30, 32, 34 to mount respective cups 18, 20, 22 in nested relation. The disclosed system provides a method of muffling and catalyzing exhaust by directing the exhaust through a plurality of catalyst-coated perforated cups 18, 20, 22, etc. The cups are stacked in nested relation, and acoustic properties are varied by varying the perforation pattern of a cup relative to the next cup. The system enables increased baffling of noise and exhaust to surface area time by non-aligning perforation patterns of adjacent cups. The system enables optimizing catalyst formulation by adding induction air between cups.

Claims: A catalytic muffler (10) comprising a housing (12) having an inlet (14), an outlet (16), and a plurality of catalyst-coated perforated cups (18, 20, 22) between said inlet (14) and outlet (16), such that exhaust flowing through said housing (12) from said inlet (14) to said outlet (16) is acoustically attenuated and catalyzed by said cups (18, 20, 22), wherein said housing (12) extends axially, wherein said cups (18, 20, 22) are stacked such that said exhaust flows serially through said cups (18, 20, 22), wherein each cup (18,20,22) has an open end (30, 32, 34), a closed end (36, 38, 40), and a closed-loop sidewall (42, 44, 46) between said open end (30, 32, 34) and said closed end (36, 38, 40), characterized in that said cups (18, 20, 22) are stacked in nested axially overlapped relation with said closed ends (36, 38, 40) adjacent each other, said sidewalls (42, 44, 46) adjacent each other in concentric relation, and said open ends (30, 32, 34) adjacent each other, said muffler (10) comprises a support structure providing a gap between said closed ends (36, 38, 40) as well as between said sidewalls (42, 44, 46), each cup (18, 20, 22) is perforated along a perforation pattern (48, 50, 52) through said closed end (36, 38, 40) and through said sidewall (42, 44, 46), and the perforation patterns of adjacent cups (18, 20; 20, 22) are non-aligned, to maximize baffling of noise and to increase exhaust to surface area time. Muffler according to claim 1, characterized in that said muffler (10) comprises at least three said cups (18, 20, 22), a first cup (18)being nested into a second cup (20) which is nested into a third cup (22), wherein the perforation pattern (48) through said sidewall (42) of said first cup (18) is circumferentially distally opposite the perforation pattern (50) through said sidewall (44) of said second cup (20), and wherein the perforation pattern (50) through said sidewall (44) of said second cup (20) is circumferentially distally opposite the perforation pattern (52) through said sidewall (46) of said third cup (22). Muffler according claim 1 or 2, characterized in that said muffler (10) includes an air induction duct (54) in said housing (12) supplying air to said gap to optimize catalyst formulation. Muffler according to any one of the preceding claims, characterized in that said support structure comprises lip flanges (56, 58,60) at said open ends (30, 32,34) engaging each other in overlapped relation such that the lip flange (56) of a first (18) of said cups engages the lip flange (58) of a second (20) of said cups to locate and suspend said first cup (18) within said second cup (20), and/or that said support structure comprises raised shoulders (62, 64) on said closed end engaging the closed end (36, 38) of the next cup to locate and space adjacent cups, and/or that said support structure comprises a mounting plate (66) mountingly engaging said open ends (39, 32, 34) to mount said cups (18, 20, 22) in said nested relation.

Inventors: BADEAU KURT M A, SCHUHMACHER KORY J, BADEAU, KURT M. A., SCHUHMACHER, KORY J.
Applicants: FLEETGUARD INC, FLEETGUARD, INC.
Application year: 2001
Main classification: F01N3
IPC codes: F01N1, F01N3, B01D53, G10K11