U.S. patent application number 10/633268 was filed with the patent office on 2005-07-21 for exhaust muffler.
Invention is credited to Wirtz, Robert B..
Application Number | 20050155818 10/633268 |
Document ID | / |
Family ID | 27798323 |
Filed Date | 2005-07-21 |
United States Patent
Application |
20050155818 |
Kind Code |
A1 |
Wirtz, Robert B. |
July 21, 2005 |
Exhaust muffler
Abstract
An exhaust muffler is provided for a motor in a hand held,
portable implement such as a power chain saw, a disc grinder or
cut-off machine, or the like, and includes a muffler housing that
encloses at least one damping chamber. The housing has an inlet for
exhaust gases from the motor, and an outlet. To improve the
noise-absorbing or dampening properties of the muffler, it has a
resonator chamber that is closed off so as to be substantially
fluid-tight relative to the damping chamber. A resonance pipe that
conveys exhaust gas is guided through the resonator chamber. An
acoustic link is provided between the resonance pipe and the
resonator chamber, and can be formed, for example, by openings or
orifices in the resonance pipe.
Inventors: |
Wirtz, Robert B.; (Essen,
DE) |
Correspondence
Address: |
ROBERT W. BECKER & ASSOCIATES
Suite B
707 Highway 66 East
Tijeras
NM
87059
US
|
Family ID: |
27798323 |
Appl. No.: |
10/633268 |
Filed: |
August 1, 2003 |
Current U.S.
Class: |
181/269 ;
181/268 |
Current CPC
Class: |
F01N 1/006 20130101;
F01N 1/02 20130101; F01N 2590/06 20130101 |
Class at
Publication: |
181/269 ;
181/268 |
International
Class: |
F01N 001/08 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 2, 2002 |
DE |
102 35 408.1 |
Claims
I claim:
1. An exhaust muffler for a motor in a hand held, portable
implement, comprising: a muffler housing that encloses at least one
damping chamber and has an inlet for exhaust gases from the motor
and an outlet, wherein a resonator chamber is provided in said
housing and is closed off so as to be substantially fluid-tight
relative to said at least one damping chamber, wherein a resonance
pipe that conveys exhaust gases is guided through said resonator
chamber, and wherein a acoustic link is provided between said
resonance pipe and said resonator chamber.
2. An exhaust muffler according to claim 1, wherein in a direction
of flow of exhaust gas, said resonance pipe is disposed between
said at least one damping chamber and said outlet.
3. An exhaust muffler according to claim 1, wherein said resonance
pipe is provided with orifices to form said acoustic link to said
resonator chamber.
4. An exhaust muffler according to claim 3, wherein a total surface
area of said orifices of said resonance pipe ranges from 200 to 500
mm.sup.2, especially 350 to 400 mm.sup.2.
5. An exhaust muffler according to claim 3, wherein said orifices
of said resonance pipe are circular and have a diameter ranging
from 1 to 4 mm, especially approximately 2 mm.
6. An exhaust muffler according to claim 3, wherein said resonance
pipe is provided with 100 to 150, especially approximately 120, of
said orifices.
7. An exhaust muffler according to claim 3, wherein said resonance
pipe extends in a curved manner in said resonator chamber.
8. An exhaust muffler according to claim 3, wherein an end of said
resonance pipe that is remote from at least one damping chamber
forms said outlet.
9. An exhaust muffler according to claim 3, wherein said inlet and
said outlet are disposed approximately across from one another.
10. An exhaust muffler according to claim 3, wherein said muffler
housing comprises two half shells, namely a bottom shell that
includes said inlet, and a top shell.
11. An exhaust muffler according to claim 10, wherein said
resonator chamber is formed by a resonator chamber shell that is
connected in a fluid-type manner with one of said half shells of
said housing.
12. An exhaust muffler according to claim 11, wherein said
resonator chamber shell is connected with said top shell.
13. An exhaust muffler according to claim 11, wherein said
resonator chamber shell is connected with said half shell by
brazing.
14. An exhaust muffler according to claim 9, wherein an end 18 of
said resonance pipe that faces at least one damping chamber has a
spacing relative to said resonator chamber.
15. An exhaust muffler according to claim 14, wherein said spacing
is at least 30% of a height of said muffler housing, and wherein
said height is the greater extension of said housing in a joining
plane of said two half shells.
16. An exhaust muffler according to claim 14, wherein a portion of
said resonance pipe that projects out of said resonator chamber
into said at least one damping chamber extends approximately
parallel to a joining plane of said two half shells, and wherein a
longitudinal central axis of said resonance pipe extends
approximately in a direction of a height of said exhaust
muffler.
17. An exhaust muffler according to claim 3, wherein said resonator
chamber is disposed within said muffler housing.
18. An exhaust muffler according to claim 3, wherein said resonator
chamber is packed with glass fibers, especially glass wool.
19. An exhaust muffler according to claim 3, wherein two damping
chambers are provided that are separated from one another by a
partition, and wherein a catalytic converter is disposed in said
partition.
20. An exhaust muffler according to claim 19, wherein in a
direction of flow of exhaust gas, said resonator chamber is
disposed in that damping chamber that is disposed downstream.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to an exhaust muffler for a
motor of a handheld, portable power tool such as a motor-driven
chain saw, a disc grinder or the like.
[0002] An exhaust muffler for a motor of a handheld power tool is
known from patent specification DT 25 39 516 A1. The exhaust
muffler has a damping chamber in a housing. An inlet opens into the
damping chamber and an outlet leads out of the damping chamber.
[0003] The underlying objective of the invention is to propose an
exhaust muffler of the generic type, which has good sound
absorption properties.
[0004] This objective is achieved by an exhaust muffler having a
muffler housing that encloses at least one damping chamber and has
an inlet for exhaust gases for the motor and an outlet, wherein a
resonator chamber is provided and is closed off so as to be
substantially fluid-tight relative to the damping chamber, wherein
a resonance pipe that conveys exhaust gas is guided through the
resonator chamber, and wherein an acoustic link is provided between
the resonance pipe and the resonator chamber.
[0005] The fact that the resonator chamber is acoustically linked
to the resonance pipe secures an additional silencing effect. At
the same time, there is essentially no flow of fluid from the
resonance pipe into the resonator chamber. The resonator chamber
absorbs particularly high frequencies in the range of from 1000 Hz
to approximately 2500 Hz.
[0006] The resonance pipe is expediently disposed between the
damping chamber and the outlet in the flow direction of the exhaust
gases. The exhaust gas temperature in the resonator chamber is
therefore relatively low, which means that the resonator chamber
can be packed with glass wool, for example. The acoustic link is
expediently provided in the form of orifices in the resonance pipe.
In order to obtain effective noise absorption, the total surface
area of the orifices is approximately 200 mm.sup.2 to 500 mm.sup.2,
in particular from 350 mm.sup.2 to 400 mm.sup.2. To make
manufacturing easier, the orifices are circular in shape. The
diameter of the orifices is expediently between 1 mm and 4 mm, in
particular approximately 2 mm. Good noise-absorbing properties are
obtained if the resonance pipe has 100 to 150, in particular
approximately 120, orifices leading to the resonator chamber.
[0007] The resonance pipe in the resonator chamber expediently runs
in a bent arrangement. In particular, the end of the resonance pipe
remote from the damping chamber forms the outlet. The exhaust gases
therefore leave the muffler after flowing through the resonance
pipe. The resonator chamber constitutes the last stage of noise
absorption. Good noise absorption is achieved as a result. This is
also a simple way of providing the outlet. The inlet and outlet are
arranged more or less opposite one another. The muffler housing is
expediently made from two half-shells, namely a bottom shell
incorporating the inlet and a top shell. The exhaust muffler can be
easily manufactured with few parts due to the fact that the
resonator chamber is provided in the form of a resonator chamber
shell, which has a flow connection to a half-shell of the muffler
housing, in particular the top shell. The connection is expediently
brazed to render it fluid-tight.
[0008] The end of the resonance pipe directed towards the damping
chamber is disposed at a distance from the resonator chamber.
Before reaching the resonator chamber, the exhaust gases therefore
have to pass along a specific path in the resonance pipe. This
further improves the noise-absorption properties. The distance is
expediently at least 30% of the height of the muffler housing, so
that the height constitutes the greater part of the muffler housing
extension in the joining plane of the two half-shells. Having an
approximately rectangular cross section in the joining plane, the
height is therefore the longer side of the rectangle. The length of
resonance pipe projecting into the damping chamber advantageously
extends substantially parallel with the joining plane of the two
half-shells, the longitudinal mid-axis of the resonance pipe
specifically extending substantially in the direction of the height
of the exhaust muffler. Exhaust gases are therefore unable to flow
into the resonance pipe until they have passed through the damping
chamber. Furthermore, the flow must change direction before flowing
into the resonance pipe. The resonator chamber is expediently
disposed inside the muffler housing. The mounting space needed for
an exhaust muffler with resonator chamber is therefore no different
from the mounting space needed for an exhaust muffler with no
resonator chamber. Incorporating the resonator chamber improves
noise absorption while requiring no extra mounting space. To obtain
efficient noise-absorption properties, the resonator chamber is
also packed with glass fiber, in particular glass wool.
[0009] The muffler advantageously has two damping chambers, which
are separated from one another by a dividing wall, a catalytic
converter being provided in the dividing wall. The resonator
chamber is advantageously disposed in the damping chamber
downstream in the flow direction of the exhaust gases.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] An embodiment of the invention will be described as an
example below with reference to the appended drawings. Of
these:
[0011] FIGS. 1-3 are perspective views of an exhaust muffler,
[0012] FIG. 4 is an exploded diagram of the exhaust muffler
illustrated in FIGS. 1 to 3,
[0013] FIG. 5 is a side view of the exhaust muffler illustrated in
FIGS. 1 to 3,
[0014] FIG. 6 is a section taken along line VI-VI in FIG. 5,
[0015] FIG. 7 is a section taken along line VII-VII in FIG. 5,
[0016] FIG. 8 is a section taken along line VIII-VIII in FIG.
6,
[0017] FIG. 9 is a side view of the resonance pipe of the muffler
illustrated in
[0018] FIGS. 1 to 8 in the direction of arrow IX in FIG. 10,
[0019] FIG. 10 is a side view of the resonance pipe of the exhaust
muffler illustrated in FIGS. 1 to 8, and
[0020] FIG. 11 is a side view of the resonance pipe in the
direction of arrow XI in FIG. 10.
[0021] The exhaust muffler 1 illustrated in the perspective
diagrams of FIGS. 1 to 3 has a muffler housing 2 into which an
inlet 3 leads. The inlet 3 is provided in the form of a
substantially rectangular orifice and opens into the damping
chamber 5 illustrated in FIG. 6. Fixing or mounting orifices 28 are
provided on either side of the inlet 3, by which the exhaust
muffler 1 is attached to a motor, in particular a motor of a
handheld portable power tool such as a motor-driven chain saw or a
disc grinder. A tubular outlet 4 leads out of the exhaust muffler
1. The muffler housing 2 is essentially made from two half-shells.
The bottom shell 10, directed towards the motor and incorporating
the inlet 3, has two reinforcing beads 24 extending substantially
parallel. The top shell 9 is remote from the motor and has a
cruciform reinforcing bead 25, which lies more or less opposite the
two parallel reinforcing beads 24. The two half-shells 9, 10 are
joined to one another at their rims 14, 13, the rim 13 of the
bottom shell 10 being turned over in a bead to engage around the
rim 14 of the top shell 9.
[0022] As may be seen from the exploded diagram shown in FIG. 4, a
peripheral gasket 12 is provided between the rims 13, 14. Disposed
inside the muffler housing 2 is a resonator chamber shell 11,
through which a resonance pipe 7 leads. Sleeves or tubes 15 are
inserted through the muffler housing 2 at either side of the
resonance pipe 7 and have a widened rim 29 at their end directed
towards the top shell 9. Both the top shell 9 and the bottom shell
10 have lateral raised areas 30 extending substantially
perpendicular to the rims 13, 14 of the half-shells, increasing
their strength. The resonator chamber shell 11 has a peripheral rim
31, by which it is secured to the top shell 9. The resonator
chamber shell 11 has an orifice 32, the contour of which matches
the external contour of the resonance pipe 7.
[0023] As may be seen more particularly from the section
illustrated in FIG. 6, a part of the longitudinal extension of the
resonance pipe 7 is disposed inside the resonator chamber 6 formed
in the resonator chamber shell 11. The resonator chamber shell 11
is sealed off from the damping chamber 5 formed in the muffler
housing 2 so as to be fluid-tight. The resonator chamber shell is
closed off by the top shell 9. To this end, the rim 31 of the
resonator chamber shell 11 is joined to the top shell by brazing.
For practical purposes, however, other types of joints could be
used. In the region of the resonator chamber 6, the resonance pipe
7 has a plurality of orifices 8 providing an acoustic link between
the interior of the resonance pipe 7 and the resonator chamber 6.
The volume of the resonator chamber 6 is smaller, in particular
significantly smaller, than that of the damping chamber 5. The
volume of the resonator chamber 6 is advantageously a fraction of
the volume of the damping chamber 5.
[0024] The resonance pipe 7 projects out of the resonator chamber 6
into the damping chamber 5. The end 18 of the resonance pipe 7
disposed in the damping chamber 5 therefore sits at a distance a
from the resonator chamber shell 11. The distance a is expediently
at least 30% of the height h indicated in FIG. 5. The height h is
the bigger extension of the exhaust muffler 1 in the joining plane
23 of the half-shells 9 and 10. In terms of the substantially
rectangular cross section of the muffler housing 2 in the joining
plane 23, the height h constitutes the long side of a rectangle
delineating the cross section. The run 22 of the resonance pipe 7
lying in the damping chamber 5 outside of the resonator chamber 6
is fixed by means of the web or stay 17 spot-welded onto the top
shell 9. The web 17 is brazed onto the end 18 of the resonance pipe
7 projecting into the interior of the muffler housing 2. The
longitudinal mid-axis 21 in the run 22 extends substantially
parallel with the joining plane 23, in particular substantially in
the direction of the height h. The resonance pipe 7 constitutes the
outlet 4 from the exhaust muffler 1. The resonance pipe 7 extends
in a bent arrangement inside the resonator chamber 6. A
pull-through piece or passage 16 is formed in the top shell 9,
through which the resonance pipe 7 leads. Relative to a line 33
perpendicular to the joining plane 23, the longitudinal mid-axis 21
of the resonance pipe 7 at the outlet 4 is inclined at an angle
.beta., which is expediently in the range of between 5.quadrature.
and approximately 20. However, it may also be expedient to provide
a different angle of inclination. The longitudinal mid-axis 21
intersects with the top shell 9 in the region of the outlet 4 at a
distance e from the longitudinal mid-axis 34 of the tubes 15,
simultaneously constituting the mid-axis of the inlet 3, which is
expediently in the range of from 20 mm to 40 mm.
[0025] As illustrated in FIG. 5, a tab 19 is provided at the rims
13, 14 of the half-shells 9, 10 and has a central fixing or
mounting orifice 20. The width b of the exhaust muffler 1 as
measured in the joining plane 23 is smaller than the height h. When
a power tool is disposed in the normal operating position, the
height h extends in the vertical direction in the standard
assembled position.
[0026] As may be seen from the section illustrated in FIG. 7, the
longitudinal mid-axis 34 of the tubes 15 forms an angle .alpha.
with the line 33 perpendicular to the joining plane 23 which may be
between 50 and 400, in particular approximately between 20.degree.
and 30.degree.. The reinforcing beads 24 are provided in the form
of raised areas and the reinforcing bead 25 as a recess. The inlet
3 as well as the orifices 28 disposed on either side of the inlet 3
are at a distance c from the joining plane 23 is expediently in the
range of between 30 mm and 60 mm. As may also be seen from the
section illustrated in FIG. 8, the tubes 15 are pushed from the top
shell 9 out through pull-through pieces or passages 27 in the top
shell 9. At their end directed towards the bottom shell 10, the
tubes 15 have a shoulder 35, which sits on a reinforcing element
26. The reinforcing element 26 is therefore disposed between the
bottom shell 10 and the shoulder 35 of the tube 15. The reinforcing
element 26 prevents the bottom shell 10 from being torn out in the
region of the fixing. In order to secure the exhaust muffler 1 to a
motor, it is screwed to the motor by means of screws, which are
pushed through the tubes 15 and project through orifices in the
reinforcing elements 26. In the region of the top shell 9, the
tubes 15 have a rim 29, which abuts with the pull-through piece 27
and retains the tube 15. The tube 15 is expediently secured to the
top shell 9 by additional means.
[0027] FIGS. 9 to 11 illustrate the resonance pipe 7. The resonance
pipe 7 has lateral rims or edges 36, which lie substantially
diametrically opposite one another. The rims 36 extend from the end
18 of the resonance pipe 7 disposed in the damping chamber 5 as far
as the point at which the resonance pipe 7 leaves the resonator
chamber 6. The terminal edges 37 of the rims 36 sit against the
internal face of the top shell 9. The position of the resonance
pipe 7 is fixed as a result. The rims 36 have a half width f, which
may be in the range of from 0.3 mm to 1.5 mm. In the region of the
resonator chamber 6, the resonance pipe 7 has a plurality of
orifices 8. The orifices 8 are circular in shape and have a
diameter d in the range of from 1 mm to 4 mm and in particular
approximately 2 mm. The resonance pipe 7 advantageously has
approximately 100 to 150, in particular about 120 orifices 8. The
total surface area of the orifices 8 is expediently 200 mm.sup.2 to
500 mm.sup.2, in particular 350 mm.sup.2 to 400 mm.sup.2. The
orifices 8 provide an acoustic link between the resonance pipe 7
and the resonator chamber 6. In order to obtain efficient
absorption or dampening, the resonator chamber 6 is completely
filled with glass fibers, in particular glass wool, or with some
other sound-absorbing material.
[0028] It may be of advantage to split the damping chamber 5 into
two damping chambers. To this end, a dividing wall extends in
particular in the joining plane 23. A catalytic converter may be
provided in the dividing wall. Instead of the circular orifices, it
would also be possible to provide other acoustic links between the
interior of the resonance pipe and the resonator chamber. The
resonator chamber may also be arranged externally to the muffler
housing 2. It might be of advantage to arrange the resonator
chamber in the region of the outlet, although it may also be
expedient to arrange the resonator chamber in the region of the
inlet to the exhaust muffler.
[0029] The invention may advantageously be used in conjunction with
low capacity motors in the range of approximately 20 cm.sup.3 to
approximately 250 cm.sup.3 piston displacement.
[0030] The specification incorporates by reference the disclosure
of German priority document 102 35 408.1 filed Aug. 2, 2002.
[0031] 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.
* * * * *