EP0271465A2

EP0271465A2 - Silencer

Info

Publication number: EP0271465A2
Application number: EP87850384A
Authority: EP
Inventors: Tore Reinhardtsen
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-12-12
Filing date: 1987-12-11
Publication date: 1988-06-15
Also published as: NO873269D0; NO873269L; EP0271465A3

Abstract

Silencer comprising an elliptic wall where an introduction pipe (1) for introduction of the sound producing medium being terminated in one of the focusing points (8) of the silencer. The silencer comprises sound absorbing material (4) and a second focusing point (7) does not have such sound absorbing material. The sound waves thereby propagating from the first focusing point (8) against the elliptic wall (3), thereby being reflected from the wall towards the second focusing point (7) and from here being propagated back to the elliptic wall (3) where the sound waves again are reflected to the first focusing point (8) are propagated further back through the introduction pipe (1). An exhaust pipe (2) for gases being arranged in a distance from the second focusing point (7).

Description

The present invention is related to a silencer according to the preamble of the claims.
Silencers of different designs are known especially in connection with muffling of sound waves from combustion engines, also ellipsoidic or elliptic silencers where the sound is liberated in one focusing point of the ellipsis and upon reflection is focused in the second focusing point where the substantial part of the sound is absorbed by a sound absorbing material.
It has now been found that a significant effect can be achieved by a silencer which at least in one plane has an elliptic wall where, according to the invention, the sound transmitting medium is liberated in the focusing point of the ellipsis and upon reflection through the second focusing point will return to the first focusing point, as defined by the features stated in the characterizing clause of the claims.
In the drawing, Fig. 1 discloses a longitudinal section through the silencer in a plane having an elliptic outer shape, Fig. 2-8 disclose different embodiments of the cross section of the silencer from a revolution body in Fig. 2, to a disc shape in Fig. 4-8, Fig. 9-13 disclose different embodiments of the silencer in a longitudinal section perpendicular to the section in Fig. 1, Fig. 14 discloses a section corresponding to Fig. 9-13, of a further embodiment, comprising a container in the first focusing point, filled with sound absorbing material, Fig. 15 discloses a section corresponding to Fig. 9-13 of an embodiment comprising another arrangement of the introduction pipe, Fig. 16 discloses a section corresponding to Fig. 1 of a further embodiment of the invention, where the sound absorbing material is arranged in an extension of the introduction pipe, Fig. 17 discloses a section corresponding to Fig. 1, of an embodiment comprising a silencer being cut in the first focusing point, Fig. 18 discloses an embodiment of the silencer where the two focusing points are overlapping and Fig. 19 discloses a section corresponding to Gi. 4-8, where the upper and lower sides of the silencer are concave.
The silencer according to the invention has an elliptical wall 3 in longitudinal section, as disclosed in Fig. 1. The silencer furthermore comprises an introduction pipe 1 terminating substantially in one of the focusing points of the ellipsis, whereas the output pipe 2 preferably is arranged in the opposite end of the silencer, for the exhaust of gases.
The silencer in Fig. 1 may have the shape of an ellipsoid with a circular cross section as disclosed in Fig. 2, an elliptical section as disclosed in Fig. 3, or a disc form as disclosed in Fig. 4-8. The elliptic wall 3 of the silencer may have inwardly from the mid plane bevelled end walls in both sides as disclosed in Fig. 5, one end wall 3 as disclosed in Fig. 4 where the disc shaped silencer is a disc of the ellipsoid in Fig. 2.
The silencer in Fig. 6 substantially corresponds to the silencer in Fig. 4, the three transitions of the end walls to the surfaces 6 of the disc, thereby being rounded. Likewise as disclosed in Fig. 7 the silencer comprises cylindric walls 3 in an elliptic shape and flat upper and lower surfaces 6, whereas Fig. 8 discloses a corresponding embodiment, however with rounded transitions between the end wall 3 and the surfaces 6 of the disc. Fig. 19 discloses a silencer comprising a substantially rectangular cross section, the upper and lower surfaces 6, however being concave.
Fig. 9-13 disclose different embodiments of the silencer in an longitudinal section perpendicularly to the section in Fig. 1. Fig. 9 and 10 disclose the silencer having against each other sloping upper and lower surfaces 6, Fig. 9 thereby having the largest distance between upper and lower surfaces at the introduction pipe and Fig. 10 the opposite shape. Fig. 11 and 12 disclose silencers where the upper and lower surfaces 6 have the same distance at the introducton and the exhaust pipes, but where the distance between them is larger in Fig. 11 and less in Fig. 12. Fig. 13 discloses a silencer having parallel upper and lower surfaces 6. Fig. 14 discloses a silencer corresponding to Fig. 13, but where a box 9 is arranged on the silencer, near the first focusing point 8, comprising an aperture 5 between the box and the internal of the silencer, substantially in the first focusing point 8. The box 9 is filled with sound absorbing material 10.
Fig. 15 discloses the introduction pipe 1 arranged in the first focusing point 8 perpendicularly to the longitudinal axes of the silencer and Fig. 16 discloses a silencer where a box 11 is arranged as an extension of the introduction pipe 1 and which is filled with sound absorbing material 12.
Fig. 17 discloses embodiment where the introduction pipe 1 for the sound, terminates at the first focusing point 8. The rear part of the ellipsis here is replaced with a wall 11 from the edge of the introduction pipe to the circumference of the ellipsis. According to the wave theory, the sound waves will follow this edge, however not be reflected from it. With such a wall 11 more sound waves can be reflected to the first focusing point 8. The wall 11 should be straight or slightly curved as disclosed in the Figure. The cross section of the wall may have a shape as described above. Fig. 18 discloses a special embodiment of the elliptical silencer where the two focusing points overlap and where the sound waves therefore are reflected directly back to the first focusing point.
As disclosed with broken line in Fig. 1, the sound waves will propagate from the first focusing point 8 against the wall 3 of the silencer and on this way move through the sound absorbing material 4 which is dampening part of the sound, whereas the rest of the sound waves will be reflected from the wall 3 and focused to the second focusing point 7 to continue against the opposite wall 3 and thereafter being reflected to the first focusing point 8. Upon this, the sound waves grately will propagate back to the sound source through the introduction pipe. The sound waves being focused therefore may be absorbed by the sound absorbing material 4 in the silencer itself, or by means of resonance dampening by means of the box 9 filled with sound absorbing material 10, as disclosed in Fig. 14. Likewise the reflected sound waves are absorbed by the sound absorbing material 12 in a separate dampening means, namely the box 11 being arranged on the introduction pipe upstreams the elliptic silencer.
The sound absorbing material may be arranged any place in the silencer and the muffling thereby will increase with the amount of material.
The exhause pipe of the silencer may be arranged anywhere however not in the focusing point 7 or 8. An arrangement as disclosed in the drawing probably will give the best result.
Principally the gas flow not necessarily has to come from the sound source itself.

Claims

1. Silencer comprising an elliptic wall (3), CHARACTERIZED IN an introduction pipe (1) for introduction of the sound giving medium, is terminating in one focusing point (8) of the ellipsis, the silencer comprising sound absorbing material (4), the second focusing point (7) not having sound absorbing material such that the sound waves propagate from the first focusing point (8) against the elliptic wall (3), here being reflected towards the second focusing point (7) from which the second waves are propagated back to the elliptic wall (3) where the sound waves again are reflected to the first focusing point (8) and thereafter being propagated back through the introduction pipe (1), and the silencer comprising an exhaust pipe (2) for gases, arranged in a distance from the second focusing point (7).

2. Silencer according to claim 1, CHARACTERIZED IN the silencer having a circular cross section, thereby creating an ellipsoid.

3. Silencer according to claim 1, CHARACTERIZED IN the silencer having an elliptical cross section.

4. Silencer according to claim 1, CHARACTERIZED IN the silencer having a rectangular cross section.

5. Silencer according to claim 4, CHARACTERIZED IN the distance between the upper and lower surfaces of the silencer decreases from the introduction pipe (1) towards the exhaust pipe.

6. Silencer according to claim 4, CHARACTERIZED IN the distance between the upper and lower surfaces of the silencer increasing from the introduction pipe (1) towards the exhaust pipe (2).

7. Silencer according to claim 4, CHARACTERIZED IN the distance between the upper and lower surfaces of the silencer having a maximum in the middle between the two focusing points (7, 8).

8. Silencer according to claim 4 CHARACTERIZED IN the distance between the upper and lower surfaces of the silencer having a minimum in the middle between the two focus ing points (7, 8).

9. Silencer according to claim 4-8, CHARACTERIZED IN the upper and lower surfaces of the silencer being concave.

10. Silencer according to claim 1-9, CHARACTERIZED IN a box (9) being arranged on the exterior of the silencer and filled with sound absorbing material (10), whereby an aperture is present between the box (9) and the interior of the silencer, in the first focusing point (8).

11. Silencer according to claim 1-10, CHARACTERIZED IN a box (11) comprising sound absorbing material (12) being arranged as an extension of the introduction pipe (1), outside the silencer, for absorbation of direct and reflected sound waves.

12. Silencer according to claim 1-11, CHARACTERIZED IN one end of the silencer being terminated by a preferably concave wall as an extension of the first focusing point (8).

13. Silencer according to claim 1-11, CHARACTERIZED IN the first (8) and second (7) focusing points overlapping each other.