US20060102420A1

US20060102420A1 - Muffler for exhaust gas

Info

Publication number: US20060102420A1
Application number: US11/272,621
Authority: US
Inventors: Bernhard Huber; Peter Götzenberger; Alfred Bothner
Original assignee: Andreas Stihl AG and Co KG
Current assignee: Andreas Stihl AG and Co KG
Priority date: 2004-11-13
Filing date: 2005-11-14
Publication date: 2006-05-18
Also published as: CN1773085A; DE102004054966A1

Abstract

A muffler with a housing having an inlet, an outlet, and at least one chamber is provided with a cleaning member that is disposed in the chamber. The cleaning member is movable relative to the housing.

Description

The instant application should be granted the priority date of Nov. 13, 2004, the filing date of the corresponding German patent application 10 2004 054 966.4.

BACKGROUND OF THE INVENTION

The present invention relates to a muffler for exhaust gas, especially in a manually guided or portable implement such as a power chain saw, a cut-off machine or the like.
EP 0 771 391 B1 discloses a muffler having two chambers formed in its housing. A catalytic converter is disposed between the first and the second chamber, and a spark arrestor is disposed at the outlet on the second chamber.
The exhaust gases that flow into the muffler also contain particles. These particles accumulate in the housing of the muffler and lead to fouling of the housing. The particles can in particular lead to a significant clogging of the spark arrestor. This necessitates frequent maintenance and frequent replacement of the spark arrestor.
It is an object of the present invention to provide a muffler that reduces fouling of the housing.

BRIEF DESCRIPTION OF THE DRAWINGS

This object, and other objects and advantages of the present invention, will appear more clearly from the following specification in conjunction with the accompanying schematic drawings, in which:
FIG. 1 is a cross-sectional view through a muffler taken along the line I-I in FIG. 2;
FIG. 2 is a cross-sectional view through the muffler of FIG. 1 taken along the line II-II in FIG. 1;
FIG. 3 is a cross-sectional view through the muffler of FIG. 2 taken along the line III-III in FIG. 2;
FIG. 4 is a cross-sectional view through a muffler taken along the line IV-IV in FIG. 5;
FIG. 5 is a cross-sectional view through the muffler of FIG. 4 taken along the line V-V in FIG. 4;
FIG. 6 is a cross-sectional view through the muffler of FIG. 5 taken along the line VI-VI in FIG. 5;
FIG. 7 is an enlarged view of the encircled portion VII in FIG. 4; and
FIGS. 8-12 are perspective views of cleaning members.

SUMMARY OF THE INVENTION

The muffler of the present application comprises a housing having an inlet, an outlet, and at least one chamber, and also comprises a cleaning member that is disposed in the chamber, with the cleaning member being movable relative to the muffler housing.
Due to the pressure fluctuations in the housing, the movable cleaning member is thrown or hurled back and forth in the chamber. The striking or impact of the cleaning member, for example against the inner wall of the housing or against a spark arrestor, loosens the particles that have accumulated on the wall or have adhered thereto. These loosened particles are then conveyed out of the muffler together with the exhaust gases. The cleaning member thus continuously effects an automatic or self cleaning of the muffler. The cleaning member can have a simple construction as well as a low weight, so that in particular in manually guided implements the overall weight of the implement is not noticeably affected. The sound that results when the cleaning member strikes against a wall can, by suitable selection of the cleaning member, be balanced such that the generation of noise is minimal relative to the operating noise of the internal combustion engine.
A straightforward design results if the cleaning member is freely movable in the chamber. By means of suitable selection of the inner geometry of the chamber, and the outer geometry of the cleaning member, it is possible to completely clean the chamber with the cleaning member. However, it can also be advantageous to guide the cleaning member with play in the chamber. In particular, the cleaning member can be arranged in such a way that it cleans regions that are particularly susceptible to being fouled. The outer surface of the cleaning member is advantageously guided with play against the inner wall of the chamber.
To prevent discharge of glowing particles from the muffler, and to satisfy local regulations, a spark arrestor is disposed at the outlet out of the chamber. By disposing the cleaning member in the chamber in which the spark arrestor is disposed, fouling of the spark arrestor can be reduced. The spark arrestor is in particular cylindrical, and the cleaning member is advantageously guided with play on the periphery of the spark arrestor. During operation of the muffler, dirt particles can easily accumulate or adhere to the spark arrestor. To prevent clogging of the spark arrestor, it must be replaced on a regular basis. By disposing a cleaning member on the spark arrestor, dirt particles are continuously removed from the spark arrestor during operation, so that the maintenance intervals can be considerably increased.
The cleaning member is in particular supported between the chamber wall and the spark arrestor. The play relative to the inner wall of the chamber is advantageously greater than the play relative to the spark arrestor. Thus, during operation, the cleaning member preferably strikes against the spark arrestor and cleans it. If the vibrations are strong, the inner wall of the chamber forms a stop or abutment for the cleaning member, so that the spark arrestor cannot be deformed or destroyed by the cleaning member. The cleaning member is advantageously movable in a peripheral direction relative to the spark arrestor. It can be advantageous for the cleaning member to be movable in the axial direction of the spark arrestor. The cleaning member is in particular movable not only in the axial direction but also in the peripheral direction relative to the spark arrestor.
A straightforward embodiment results if the cleaning member is a coil spring. The corrugated structure of the coil spring formed by the spring windings leads to a good loosening or removal of dirt particles. However, it can also be expedient for the cleaning member to be a ring. This ring is advantageously provided with a slot. The cleaning member is advantageously also provided with at least one opening or aperture. The slot or aperture or apertures improve the cleaning effect of the member. If the slot is large enough, it is also possible to mount the cleaning member on the spark arrestor in the radial direction relative to the spark arrestor.
The housing of the muffler is advantageously formed from two half shells between which is disposed a partition that separates a first chamber from a second chamber. A catalytic converter can in particular be disposed in the partition. A third half shell is advantageously disposed on the partition and forms a third chamber with the partition. Disposing a plurality of chambers one after the other leads to a good dampening effect of the muffler. By connecting the third half shell to the partition, the third chamber can be easily formed with few additional components. The spark arrestor is in particular disposed at the outlet out of the third chamber. In this connection, the outlet out of the third chamber advantageously opens into the outlet out of the muffler.
Further specific features of the present application will be described in detail subsequently.

DESCRIPTION OF SPECIFIC EMBODIMENTS

Referring now to the drawings in detail, the muffler 1 illustrated in FIG. 1 has a housing 2, which is formed from a first half shell 3 and a second half shell 4. The two half shells 3 and 4 are interconnected at a rim 5 by being folded over. Disposed between the two half shells 3 and 4 is a partition 6 which is held at the rim 5. The partition 6 separates a first chamber 9, into which flow the exhaust gases of an internal combustion engine, especially a two-cycle engine, from a second chamber 10.
The exhaust gases flow into the muffler 1, i.e. into the housing 2 thereof, via the inlet 18, which is indicated by dashed lines in FIG. 2. As furthermore shown in FIG. 2, the partition 6 is provided with openings 20 by means of which the exhaust gases can pass out of the first chamber 9 and into the second chamber 10. As shown in FIGS. 1 and 2, two sleeves 8 extend through the housing 2 approximately perpendicular to the partition 6. On that side that faces the first half shell 3 the sleeves 8 are open, and have a base 50 on that side that faces the second half shell 4. The base 50 rests against a reinforcing plate or sheet 13 that is disposed between the second half shell 4 and the base 50. At each sleeve 8, the muffler 1 has a mounting opening 7 that extends through the base 50 of the sleeves 8, the reinforcing plate 13 and the second half shell 4. The muffler 1 can be fixed in position on the internal combustion engine at the mounting openings 7 via fastening bolts that can be tightened through the sleeves 8.
The partition 6 has a recessed portion 21 (FIGS. 1 and 3) that extends over approximately one fourth of the height, and half of the width, of the muffler 1. In this connection, the width is measured parallel to the connecting line of the two mounting openings 7, and the height is measured perpendicular thereto in the plane of the partition 6. The recessed portion 21 projects in the direction toward the first half shell 3. A third half shell 22 is positioned in the vicinity of the recessed portion 21 on the opposite side, which faces the second half shell 4; the third half shell 22 projects in the direction toward the second half shell 4. The recessed portion 21, together with the third half shell 22, forms a third chamber 11. By means of an inlet 12 in the recess portion 21, the third chamber 11 communicates with the second chamber 10. The third chamber 11 extends over nearly the entire dept of the muffler 1. The depth of the muffler 1 is measured perpendicular to the partition 6.
A cleaning member 14 is disposed in the third chamber 11. The cleaning member 14 is embodied as a tubular section, and is freely movable in the third chamber 11. A spark arrestor 15 projects into the third chamber 11. The spark arrestor 15 has a cup-shaped configuration, and therefore has a cylindrical body that is closed off by a base on that side that projects into the chamber 11. The spark arrestor 15 furthermore has a plurality of openings 23 through which the exhaust gases can flow out of the third chamber 11.
As shown in FIG. 3, the spark arrestor 15 is disposed at the outlet 28 out of the chamber 11. The spark arrestor 15 is fixed in position on an adapter 16, at which is formed the outlet 19 out of the muffler 1. An adapter 16 is screwed into a threaded sleeve 17, which is positioned in the second half shell 4. The sleeve 17 can, for example, be pressed into the second half shell 4.
During operation, the exhaust gases flow out of the internal combustion engine and into the muffler 1. In this connection, great pressure fluctuations result due to the operation of the internal combustion engine. Due to these fluctuations, the cleaning member 14 is thrown or hurled back and forth in the third chamber 11. The cleaning member 14 strikes against the wall of the chamber 11 and against the spark arrestor 15, and thereby frees in particular the spark arrestor 15 of particles that have accumulated upon the spark arrestor. The mechanical striking of the cleaning member 14 leads to a reduction in size of the particles, so that these particles pass through the spark arrestor 15 and can pass out of the muffler 1 together with the exhaust gases. This prevents the muffler 1 from becoming clogged. The spark arrestor 15 thus has to be replaced less frequently, thereby increasing the length of the maintenance intervals.
FIGS. 4 to 7 illustrate an embodiment of a muffler 31. The same reference numerals designate the same components as in FIGS. 1 to 3. The housing 2 of the muffler 1 is also formed of two half shells 3 and 4 that are interconnected at a rim 5. Fixed in position at the rim 5 is a partition 36 that separates the first chamber 9 from the second chamber 10. Positioned at the partition 36 is a third half shell 32 that together with the partition 36 delimits a third chamber 41. In the region of the third half shell 32, the partition 36 has raised portions 33 that extend from the partition in the direction toward the second half shell 4 and project into the third chamber 41. Disposed in the interior of the third chamber 41 is a spark arrestor 35 that has a plurality of openings 43. The spark arrestor 35 is also cup-shaped, and thus has a cylindrical base body that is closed off by a base 47 (FIG. 5) on that side that projects into the interior of the chamber 41. A cleaning member 34 is disposed on the periphery of the spark arrestor 35.
As shown in FIGS. 5 and 6, the cleaning member 34 is configured as a coil spring. The length of the coil spring is greater than the distance from the base 47 of the cleaning member to the wall of the chamber 41, so that the cleaning member 34 is supported on the spark arrestor 35. However, the cleaning member 34 is movable on the spark arrestor 35 in the radial direction, in the axial direction and in the peripheral direction of the spark arrestor. As a result, during operation of the muffler 31, particles that have accumulated on the spark arrestor 35 are knocked off.
During operation, the exhaust gases flow into the first chamber 9 through the inlet 18 shown in FIG. 5, and to the second chamber 10 via the openings 20 in the partition 36 as shown in FIG. 6. At the level of the third chamber 41, the partition 36 has an inlet 42 through which the exhaust gases flow into the third chamber 41 from the second chamber 10. The spark arrestor 35 has a plurality of openings 43 through which the exhaust gases flow into the interior of the spark arrestor from the third chamber 41. The spark arrestor 35 is disposed in the outlet 48 out of the third chamber 41. The outlet 48 is provided on an adapter 38, which at the same time forms the outlet 39 out of the muffler 31. The adapter 38 is screwed into a threaded sleeve 37 that is held in the second half shell 4. It is thus easy to screw the adapter 38 out of the sleeve 37 in order to be able to replace the spark arrestor 35.
The opening 49 through which the spark arrestor 35 projects into the chamber 41 is smaller than the outer diameter of the cleaning member 34. Thus, the cleaning member 34 remains in the third chamber 41 during replacement of the spark arrestor 35. The opening 49 is in particular approximately of the same magnitude as the outer periphery of the spark arrestor 35, so that only a small quantity of exhaust gas can flow back into the first chamber 9 from the third chamber 41 through the opening 49.
FIG. 7 is an enlarged view of the third chamber 41. Here it can be seen that the cleaning member 34 has a certain amount of play a relative to the spark arrestor 35. In the position of the cleaning member 34 shown in FIG. 7, where the cleaning member is concentric to the spark arrestor 35, the play a is the same over the entire inner periphery of the cleaning member 34. The cleaning member 34 also has the play b relative to the inner wall 40 of the chamber 41. The play b is present at at least three points of the chamber wall 40 that have the smallest spacing relative to the outer surface 29 of the cleaning member 34. For example, in the illustrated embodiment the cleaning member 34 has a play b relative to the two raised portions 33 of the partition 36. At the side opposite the partition 36, the third half shell 32 has two raised portions 30 that project into the chamber 41 in the direction toward the cleaning member 34. The cleaning member 34 has a play b at the two raised portions 30. Similarly, the cleaning member 34 has a play b relative to the two long sides 51 of the third half shell 32 that extend approximately perpendicular to the partition 36. In this connection, the play b is respectively measured in the radial direction relative to the cylindrical section of the spark arrestor 35. The play b is advantageously larger than the play a. As a result, during operation, the cleaning member 34 strikes merely against the spark arrestor 35 and frees it of particles. If great pressure fluctuations or strong vibrations are present, movement of the cleaning member 34 can lead to deformation of the spark arrestor 35. Therefore, in order to prevent damage to the spark arrestor 35, the play b is only slightly greater than the play a. If the spark arrestor deforms, the cleaning member 34 strikes against the inner wall 40 of the chamber 41, which thus forms a stop or abutment. This also accomplishes cleaning of the inner wall 40 of the chamber 41. The sections of the inner wall 40 of the chamber 41 that are spaced further from the cleaning member 34 do not come into contact with the cleaning member.
FIGS. 8 to 12 show embodiments of cleaning members. FIG. 8 is an enlarged perspective view of the cleaning member 34 of FIGS. 4 to 7. The cleaning member 34 is embodied as a coil spring having four coils. The coils or windings are spaced from one another by a distance c. The corrugated structure formed thereby leads to a good cleaning. The cleaning member 34 is light in weight. The axial length of the cleaning member 34 is sufficient to prevent tilting or canting of the cleaning member 34 on the spark arrestor 35.
The cleaning member 44 illustrated in FIG. 9 is embodied as a ring and has a wide slot 45 on one side. By means of the slot 45, the cleaning member 44 can be spread apart so that it can also be mounted on the spark arrestor 35 in the radial direction. The wide slot 45 leads to a low weight of the cleaning member 44. In addition, four openings or apertures 46 are provided in the cleaning member 44 so that the cleaning member 44 has only small concentrations of material. The walls of the apertures 46 provide a good cleaning result.
The cleaning member 24 shown in FIG. 10 is also embodied as a ring. It has a slot 25 that extends at an angle to the central axis 27 of the cleaning member 24. The cleaning member 24 has four openings or apertures 26, which are approximately circular.
The cleaning member 54 shown in FIG. 11 is embodied as a ring having a slot 55 that extends parallel to the central axis 57 of the cleaning member 54. The cleaning member 54 can, for example, be embodied as a tube or pipe section.
FIG. 12 shows a cleaning member 64 that is embodied as a cylindrical roller body. The cleaning member 64 has a bore 65 that extends coaxially to the central axis 67. The cleaning member 64 is advantageously disposed so as to be freely movable in a chamber in the muffler housing.
Other forms or shapes of cleaning members can also be advantageous. In addition, other forms or shapes of the spark arrestor can be expedient.
The specification incorporates by reference the disclosure of German priority document 10 2004 054 966.4 filed 13 Nov. 2004.
The present invention is, of course, in no way restricted to the specific disclosure of the specification and drawings, but also encompasses any modifications within the scope of the appended claims.

Claims

1. A muffler for exhaust gas, comprising:

a housing having an inlet, an outlet, and at least one chamber; and

a cleaning member that is disposed in said at least one chamber, wherein said cleaning member is movable relative to said housing.

2. A muffler according to claim 1, wherein said cleaning member is freely movable in said at least one chamber.

3. A muffler according to claim 1, wherein said cleaning member is guided in said at least one chamber with play.

4. A muffler according to claim 3, wherein an outer surface of said cleaning member is guided with play against an inner wall of said at least one chamber.

5. A muffler according to claim 1, wherein a spark arrestor is disposed at an outlet out of said at least one chamber.

6. A muffler according to claim 5, wherein said spark arrestor has a cylindrical configuration, and wherein said cleaning member is guided with play on a periphery of said spark arrestor.

7. A muffler according to claim 6, wherein a play of an outer surface of said cleaning member relative to an inner wall of said at least one chamber is greater than said play of said cleaning member relative to said spark arrestor.

8. A muffler according to claim 5, wherein said cleaning member is movable relative to said spark arrestor in a peripheral direction of said spark arrestor.

9. A muffler according to claim 5, wherein said cleaning member is movable in an axial direction of said spark arrestor.

10. A muffler according to claim 5, wherein said cleaning member is a coil spring.

11. A muffler according to claim 1, wherein said cleaning member is a ring.

12. A muffler according to claim 11, wherein said ring is provided with a slot.

13. A muffler according to claim 11, wherein said cleaning member is provided with at least one opening or aperture.

14. A muffler according to claim 1, wherein said housing is formed of two half shells, wherein a partition is disposed between said half shells and wherein said partition separates a first chamber from a second chamber.

15. A muffler according to claim 14, wherein a third half shell is disposed on said partition, and wherein said third half shell forms a third chamber with said partition.

16. A muffler according to claim 15, wherein a spark arrestor is disposed at an outlet out of said third chamber.