EP0171928A1

EP0171928A1 - Exhaust silencer

Info

Publication number: EP0171928A1
Application number: EP85305005A
Authority: EP
Inventors: Robert Harris
Original assignee: Individual
Current assignee: Individual
Priority date: 1984-07-13
Filing date: 1985-07-12
Publication date: 1986-02-19
Also published as: GB8417917D0; GB8517618D0; GB2161542A

Abstract

Exhaust silencer, and method for its construction, which comprises a central structure made up of one or more intermediate components (12B - 12E) each in the form of an open-topped container and the base (24A) of which is apertured as at (33) to provide a baffled pathway for exhaust gases. The assembly is completed by end caps (12A, 11A) which are mutually inverted at opposite ends of the central structure (12B - 12E) and at least one (12A) of the end caps may be similar to the intermediate component or components (12B - 12E) and similarly made by a drawing or stamping operation. At the junction between the base (24A) and the sidewall of each similar component (12A - 12E) there is a rebate (18A) which receives the periphery of an adjacent component as a friction fit. This may be reinforced by welding or brazing.

Description

This invention relates to an exhaust silencer. As currently most commonly made the relatively small silencers fitted to engines in the category of those of lawnmowers, cement-mixers, motorcycles, stationary engines and industrial engines essentially comprise a box into which the exhaust pipe opens. Between the exhaust pipe and an outlet opening of the box one or more baffle plates are welded or rivetted in the box interior after its formation.
A principal object of the present invention is to provide an improved silencer construction in which the baffle means is an integral part of the box, obviating a separate baffle locating operation, but which is nevertheless versatile in its application in being capable of taking a variety of forms.
According to one aspect of the invention there is provided a method of constructing an exhaust silencer which comprises fitting end cap components to opposite ends of a central structure which comprises an intermediate component having the form of an open-topped container, the base of said.intermediate comp- onent serving as a baffle which extends across the plenum defined by the central structure and the end caps.
In an exhaust silencer made by the method defined in the preceding paragraph preferably each end of the central structure makes a friction fit with the periphery of the respective end cap. The central structure may comprise more than one intermediate component having the form of an open-topped container, the respective base portions of the said intermediate components being adapted to serve as different baffle elements within the silencer, and the central structure may additionally comprise annular spacer components between said intermediate components chosen to give the silencer a chosen length or internal volume.
In accordance with yet another aspect of the present invention there is provided a kit of parts for the assembly of an exhaust silencer, said kit comprising a plurality of components each having the form of an open-topped container and of similar cross-sectional configuration, said components comprising at least one intermediate component and two end components which latter, in the assembled condition of the silencer, are in a mutually inverted relationship with the intermediate component between them, at least one of the components being rebated in such a way that the components will interfit with the wall of each component forming part of the wall of the assembly, the base of said intermediate component being arranged or adapted to provide a baffle within the silencer interior.
Preferred embodiments of the invention will now be described with reference to the accompanying drawings, in which:-

Figure 1 is an exploded view of a first silencer assembly,
Figure 2 is an illustration of the silencer of Figure 1, when assembled,
Figure 3 is a cross-sectional view taken between the planes A and B in Figure 2 and viewed in the direction of the arrows,
Figure 4 is an isometric view of a second silencer assembly, and
Figure 5 is a sectional elevation taken on the line V-V of Figure 4.

The hollow casing of the silencer 10 illustrated in Figures 1 - 3 is made up of two similar, mutually inverted D-section end caps 11 and 11', each having the form of an open-topped container, and intermediate sections 12,13 and 14 interposed between them. The intermediate sections 12 and 14 also have the form of open-topped containers and are mutually inverted, but in contrast to the end caps the seotions 12 and l4 have the configuration of flat-bottomed dishes. The base portion of the section 12 has a peripheral rebate 15 to receive and fit snugly within the periphery of the cap 11 and the base portion of the section l4 has a peripheral rebate 16 for similarly receiving and snugly fitting within the periphery of the end cap 11' .
In contrast to the open-topped, container- shaped sections 12 and 14 the section 13 inserted between them has neither a base nor a top but is annular, having a wall shaped so that its upper edge will fit snugly within a rebate 17 in the lower periphery of the section 12 while its lower edge is received in a similar rebate 18 in the upper periphery of the section 14.
Corresponding corners of the sections 12 and 14 have balcony- like protrusions 19A and 19B. The internal rebates 17 and 18 continue in these protrusions and the annulus 13 has a similar protrusion at 19C. Located inside the annular section 13 is yet another section 20. This also is annular (i.e. it has no top or bottom), but it is of a symmetrical, generally rectangular shape lacking the protrusion 19C. Consequently, as best seen in Figure 3, in the assembled condition of the silencer the section 20 isolates the interior of the protrusion 19A,B,C from the rest of the casing interior. In the region of the protrusion the section 20 is, however, formed with holes 21. Together with an elongated opening 22 in the protrusion 19A these holes 21 provide an escape route through the protrusion plenum for exhaust gases in the main part of the silencer interior.
An end portion 23 of the base 24 of the section 12 is cut out and bent up, and the remainder of the base 24 is perforated as at 25 to form a baffle. The greater part 27 of the base 26 of the section 14 is cut out and bent up, the free end 28 of the cut out part 27 being bent back parallel with the remainder of the base 26 to make contact with the underside of the base 24 of section 12. There is thus provided a path P for gases between the end caps 11 and 11' which avoids the baffle 25 and is adjacent the protrusion plenum 19A,B,C, communicating therewith via the holes 21. This path P, extended by the flange 23, may be closed at its bottom end by the remaining portion 26 of the base of section 14 or if desired one or more apertures (not shown) may be provided in the base portion 26 to place the path P directly in communication with the interior of the end cap 11'.
Exhaust gases may be admitted to the interior of the silencer 10 in any known way and at any chosen location. By way of example, the end cap 11' is shown as having an opening 30 to which an exhaust pipe (not shown) can be sealed so as to discharge into the end cap 11¹, whence the exhaust gases (or the greater proportion thereof) will pass upwardly through the baffle 25, have their direction changed over the flange 23 by the end cap 11, flow down the path P and finally exit through the holes 21, the plenum formed by the protrusions 19A,B,C and the opening 22.
The broken line 31 in Figure 1 is intended to illustrate the fact that it is not necessary that the top and bottom of the insert 20, or any of the intermediate sections 12,13 and 14, should be bounded by parallel planes. If they are not the silencer as a whole may be given a shape different from that shown in Figure 2 for particular purposes, e.g. to fit in a given space.
In the second embodiment of the invention illustrated in Figures 4 and 5 the silencer 10A is constructed by seating one on top of another five dish- shaped sections 12A,12B,12C,12D and 12E of similar, rounded, approximately elliptical configuration. The sections may, however, be of different wall depth as is most clear in the case of the shallower sections 12C and 12E. At the junction of the sidewall and the bottom of each section 12A - 12E is a rebate 18A which serves to receive and seat the free, upper edge of the section immediately below, and the sections are brazed together where they thus interfit. The assembly is completed by capping the uppermost section 12E with a relatively inverted dish-shaped end cap 11A, and this is removably held in place over the wall of the uppermost dish 12E by nuts and bolts 31. The peripheral rebate 18A of the lowermost section 12A is, of course, redundant in the example illustrated but is provided to show that the structure can include any chosen number of dish-shaped parts such as 12A - 12E superimposed to provide a silencer of chosen length.
The interior of the silencer 10A thus obtained, spanned at intervals by the bottoms 24A of the dish-shaped sections, is provided at chosen locations with baffles 32, holes 33 are formed at suitable locations in the bottoms 24A and cut-out portions such as 34 bent to provide a suitable flow-path through the silencer. In the example shown the cap 11A is formed with exhaust outlet openings 22A for the exit of gases which have entered through a fixing hole 30A.
It will be apparent that many modifications of the invention are possible. The silencers illustrated are relatively complex and simpler forms of the invention utilising fewer components of simpler shape are envisaged. It is to be noted that each of the components of the silencers illustrated may be made by stamping or drawing sheet metal without any necessity for welding separate baffle plates in the interior of the silencer. Assembly is simplified and a more reliable seal is ensured by the friction fit of the.components, which may be augmented by soldering or brazing.

Claims

1. A method of constructing an exhaust silencer (10,10A) characterised in that it comprises fitting end cap components (11,11',11A,12A) to opposite ends of a central structure which comprises an intermediate component (12,14,12B-12E) having the form of an open-topped container, the base (24,26,24A) of said intermediate component serving as a baffle which extends across the plenum defined by the central structure and the end caps (11,11',11A,12A).

2. A method as claimed in claim 1, characterised in that each said component (11,11', 12,14) is made by stamping or drawing sheet metal and the construction of the silencer is effected without welding in the silencer interior.

3. A method as claimed in claim 1 or claim 2, characterised in that a rebate (15,16,18A) is formed in at least one said component (12,14,12B-12E) to receive a periphery of another of said components in a seated and interfitted relationship.

4. A method as claimed in claim 3, characterised in that the rebate (15,16,18A) is provided around the or each intermediate component (12,14,12B-12E) at the junction between the base (24,26,24A) and the sidewall thereof, and is dimensioned to receive the periphery of an end cap (11,11',12A) as a friction fit.

5. A method as claimed in claim 4, characterised in that it comprises soldering or brazing said end cap (11,11',12A) periphery in said rebate (15,16, 18A).

6. A method as claimed in any one of the preceding claims, characterised in that it comprises including in the central structure one or more intermediate components (13,20) of annular configuration, the opposite ends of the or each annular component (13,20) interfitting with intermediate components (12,14) having bases by means of rebates (17,18) formed in the sidewalls of said intermediate components (12,14) having bases, which rebates (17,18) receive as a friction fit the respective peripheries of the associated annular components (13,20).

7. An exhaust silencer made by the method claimed in any one of the preceding claims, characterised in that it comprises mutually inverted end caps (11,11'), two mutually inverted intermediate components (12,14) each in the form of an open-topped container and an annular intermediate component (13) interposed between the first-mentioned intermediate components(12,14), all of the components and end caps interfitting by means of the reception of the periphery of one as a friction fit in a rebate (15,16,17, 18) in another, the bases (24,26) of the mutually inverted intermediate components (12,14) being cut and/or perforated to provide a baffled path for exhaust gases through the silencer.

8. An exhaust silencer as claimed in claim 7, characterised in that the base (24) of one (12) of the mutually inverted intermediate components has a perforated portion (25) and a portion (23) which is cut out and bent at right-angles to the perforated portion (25) and the base (26) of the other of the mutually inverted'intermediate components is imperforate but has a portion (27)approximately equal in area to said perforated portion (25) which is cut out and bent to make contact with the perforated base (24) thereby to provide parallel passages (P) for the reverse flow of exhaust gases through the silencer on opposite sides of the bent portion (27) of the imperforate base (26).

9. An exhaust silencer made by the method claimed in any one of claims 1 - 8, characterised in that it comprises a plurality of superimposed components (12A-12E) each in the form of an open-topped container and each having, at the junction between the base (24A) and sidewall thereof, a rebate (18A) to receive the periphery of the next- below component as a friction fit, those bases (24A) of the components (12B-12E) which span the interior of the silencer (10A) being apertured and there being interposed between the bases (24A) of an adjacent pair of the components (12A-12E) perforated baffle elements (32) in register with a respective aperture (30A-33) in one of said bases (24A) to provide a baffled flow-path for exhaust gases through the _ silencer (10A).

10. An exhaust silencer as claimed in claim 9, characterised in that a cap (11A) in inverted relation to the superimposed components (12A-12E) is fitted over the one (12E) of the latter which has an exposed periphery, the cap (11A) having an apertured sidewall (22A) for the escape of exhaust gases from the silencer (10A) interior.