EP0229148B1

EP0229148B1 - Silencer

Info

Publication number: EP0229148B1
Application number: EP86904417A
Authority: EP
Inventors: Tore Reinhardtsen
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-06-27
Filing date: 1986-06-26
Publication date: 1989-02-01
Also published as: NO870802L; WO1987000241A1; AU6120886A; NO852587L; NO156384C; NO164935B; EP0229148A1; DE3662010D1; NO870802D0; NO164935C; ATE40582T1; NO156384B

Abstract

Silencer comprising a closed container comprising a side wall (3) having an elliptical shape, a top, a bottom and an input (1) and an output (2). Exhaust gases from a combustion engine are brought into the interior of the container at a first focusing point (4), and being collected in a second focusing point (5) after reflection from the side wall (3). In the second focusing point (5) a sound absorbing material (6) absorbs the sound waves and the gases thereafter exits the silencers through the output (2).

Description

The present invention is concerned with a silencer, especially for muffling sound waves form combustion engines.
Different types of silencers have been developed for muffling sound waves from combustion engines, especially in connection with automo- bils. Silencers requiring just little space and having designes which provide manufacturing at low cost has been required during a long period of time. Many attends have been made to fullfill this aim.
Silencers of the type described are known from DE-C-338 906 and NO-C-56 196. The silencer according to the first mention patent comprises a house having two against eachother facing and to eachother connected parabolic hollow members where the exhaust gases are brought in near one or both focusing points. From the focusing point the sound waves will be reflected on the internal wall and deflected to parallel beams which at the opposite internal wall are deflected and directed against the second parabolic focusing point. At this known silencer, a dampening of the noice is aimed at by mixing and swirling of the sound beams, whereby an extension of the cross section area is present from the focusing points towards the middle of the device. The known silencer has a comparatively complicated construction and an interference between different sound waves must be established to achieve effectivety.
With the silencer according to the present invention, effective dampening of the sound is achieved with a simple design according to the features stated in the characterizing clause of the claims.
In the drawings prefered embodiments are disclosed, whereby Fig. 1 discloses a section I-I in Fig. 2, Fig. 2 discloses a section II-II in Fig. 1, Fig. 3 discloses a section corresponding to Fig. 2 of a second embodiment having another arrangement of the input, Fig. 4 discloses a section corresponding to Fig. 2 of a further embodiment of the invention, Fig. 5-7 are righthand use of the silencer on Fig. 2, disclosing different side wall designes, Fig. 8-11 are sections corresponding to Fig. 2 disclosing different designs of the top and bottom of the silencer according to the invention and Fig. 12 discloses a section according to Fig. 1 of a further embodiment of the silencer according to the invention.
The silencer according to the present invention comprises, as principally disclosed in Fig. 1, an input 1 for gases transmitting sound waves, an output 2 for the exhaust, a closed container comprising a top 7, a bottom 8 and a surrounding side wall 3, and a sound absorbing material 6.
The side wall 3 has the shape of an ellipses, whereby the input 1 terminates approximately at the first focusing point 4 and sound absorbing material is arranged on and around the second focusing point 5.
The combustion gases from a not shown combustion engine are brought into the container through the input 1 in such a way that the sound waves are dispersed substantially from the first focusing point 4 in all directions, thereby being reflected from the side wall 3 and directed against" the second focusing point 5 where the sound waves substantially are absorbed. Part of the sound waves is directed also straight forward from the input 1 and thereby being absorbed by the sound absorbing material 6 directly.
The input 1 may be arranged as disclosed in Fig. 2 or as disclosed in Fig. 3, in both cases however, the sound waves will enter the container substantially in the first focusing point 4.

Fig. 4 discloses an embodiment of the present invention where the amount of sound absorbing material is increased by a box 9 arranged on the top 7 of the container, an aperture 10 thereby being provided substantially in the second focusing point 5, whereby the box 9 is completely filled with sound absorbing material.
Figures 5, 6 and 7 disclose different side wall shapes, whereby the side wall 3 according to Fig. 5 is straight between the top 7 and the bottom 8 except for a rounding connection between the wall and the top and the bottom respectively.
Fig. 6 discloses a side wall shape being part of a circle, e. g. the embodiment according to Fig. 6 thereby being a disc cut out of an ellipsoid.
The embodiment according to Fig. 7 comprises a side wall configuration where the side wall is tapered from the middle section of the silencer up to the top 7, and from the middle section down to the bottom 8.
Instead of the top and the bottom 8 being parallel as disclosed in Figures 2-4, the mutual constellation can be according to Figures 8-11. In Fig. 8 the distance between the top 7 and the bottom 8 increases from the input side against the output side, in Fig. 9 the distance decreases in the same direction.
Fig. 10 discloses an embodiment where the distance between the top and the bottom 8 decreases both from the input side and the output side against the middle of the silencer and in Fig. 11 the distance between the top 7 and the bottom 8 increases from both the input side and the output side against the middle of the silencer.
Fig. 12 discloses an embodiment having a substantial part of the container filled with sound absorbing material 6. The amount and arrangement of the sound absorbing material 6 is a matter of modifications, however is important that at least the area at and near the second focusing point 5 is filled out with sound absorbing material 6.

The input 1 principally is a pipe extending through the side wall 3 and as far as to the first focusing point 4. The input pipe, however, can be drawn back as far as to the sidewall 3 without extending into the interior of the container. Principally this is disclosed in Fig. 3 where the input is terminated at the container wall, in this case the bottom 8.
Tests have proved that the side wall shape, for example as disclosed in Figures 5-7 will have miner influence on result as opposed to the principal shape of the side wall 3 as disclosed in Fig. 1 and 12, where the elliptical shape of the side wall ensures the refection of the sound waves principally from the first focusing point 4, whereby the sound waves are focused in the second focusing point 5 after having been reflected from the side wall, except for the sound waves travelling directly from the first focusing point 4 to the sound absorbing material 6.

Claims

1. Silencer, especially for muffling sound waves from combustion engines, characterized in a closed container having a top (7) and a bottom (8) and a side wall (3) connecting the top and the bottom and having an elliptical shape in the middle longitudinal section between the top and the bottom, an input (1) for gases transmitting the sound approximately at a first focusing point (4), an output (2) near the second focusing point (5) of the ellipses, and a sound, absorbing material (6) extending from the top to the bottom, at least in the second focusing point (5) of the ellipses, which sound absorbing material (6) thereby being adapted for substantially absorbing the sound.

2. Silencer according to claim 1, characterized in the bottom (8) and the top (7) both being flat and arranged at an angle, the mutual distance thereby increasing from the input side with the first focusing point (4), towards the output side with the second focusing point (5).

3. Silencer according to claim 1, characterized in the bottom (8) and the top (7) being flat and arranged at an angle, the mutual distance thereby decreasing from the input at the first focusing point (4), towards the output side at the second focusing point (5).

4. Silencer according to claim 1, characterized in the bottom (8) and the top (7) being flat and arranged parallelly to eachother.

5. Silencer according to claim 1, characterized in the bottom (8) and the top (7) having an increasing distance from the focusing points (4, 5) towards the center area between the focusing points.

6. Silencer according to claim 1, characterized in the bottom (8) and the top (7) having an decreasing distance from the focusing points (4, 5) towards the centerarea between the focusing points.

7. Silencer according to the claim 1-6, characterized in a box (9) containing sound absorbing material, being arranged on the top, an aperture (10) in the top at the second focusing point (5), thereby connecting the sound absorbing material (6) at the second focusing point (5) with the sound absorbing material of the box (9), and increasing the total amount of the sound absorbing material.

8. Silencer according to 1-7, characterized in the sound absorbing material (6) occupying a substantial portion of the container volume.

9. Silencer according to claim 1-7, characterized in the sound absorbing material (6) having a cylindrical shape around the second focusing point (5).

10. Silencer according to claims 1-9, characterized in the side walls (3) being straight between bottom (8) and top (7).

11. Silencer according to claims 1-9, characterized in the side walls (3) between bottom (8) and top (7) being part of an ellipsoide.

12. Silencer according to claims 1-9, characterized in the side walls (3) being tapered inwardly from the container middle section towards the bottom (8) and towards the top (7).