U.S. patent application number 10/580519 was filed with the patent office on 2007-04-12 for silencer for exhaust systems.
This patent application is currently assigned to Emmett Limited. Invention is credited to Malcolm Douglas Emmett.
Application Number | 20070080020 10/580519 |
Document ID | / |
Family ID | 29797785 |
Filed Date | 2007-04-12 |
United States Patent
Application |
20070080020 |
Kind Code |
A1 |
Emmett; Malcolm Douglas |
April 12, 2007 |
Silencer for exhaust systems
Abstract
A silencer 1 for an exhaust system comprising a fluid outlet
(14, 5) and control means for opening and closing the fluid outlet
(14, 5). The control means may comprise a bi-metallic strip (2)
with a rivet stopper (22) at one end. The fluid outlet may comprise
an aperture (14) or a self-tapping plug (5).
Inventors: |
Emmett; Malcolm Douglas;
(Essex, GB) |
Correspondence
Address: |
ANDERSON, LEVINE & LINTEL L.L.P.
14785 PRESTON ROAD
SUITE 650
DALLAS
TX
75254
US
|
Assignee: |
Emmett Limited
Benfleet
GB
SS7 1RT
|
Family ID: |
29797785 |
Appl. No.: |
10/580519 |
Filed: |
November 25, 2004 |
PCT Filed: |
November 25, 2004 |
PCT NO: |
PCT/GB04/04976 |
371 Date: |
May 24, 2006 |
Current U.S.
Class: |
181/237 |
Current CPC
Class: |
F01N 3/005 20130101;
F01N 1/165 20130101; Y02T 10/12 20130101 |
Class at
Publication: |
181/237 |
International
Class: |
F01N 1/16 20060101
F01N001/16 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 25, 2003 |
GB |
0327401.6 |
Claims
1. A silencer for an exhaust system comprising a fluid outlet and
control means for opening and closing the fluid outlet.
2. A silencer according to claim 1 arranged such that when the
exhaust system is in use, the fluid outlet is opened by the control
means and when the exhaust system is idle, the fluid outlet is
closed by the control means.
3. A silencer according to claim 1 arranged such that when the
exhaust system is in use, the fluid outlet is closed by the control
means and when the exhaust system is idle, the fluid outlet is
opened by the control means.
4. A silencer according to claim 1 wherein the fluid outlet is an
aperture formed in the casing of the silencer.
5. A silencer according to claim 1 wherein the fluid outlet is a
self-tapping plug.
6. A silencer according to claim 1 wherein the control means
comprises temperature dependent control means arranged to open and
close the fluid outlet in dependence on the temperature of the
silencer.
7. A silencer according to claim 6 wherein the temperature
dependent control means comprises a bi-metallic strip.
8. A silencer according to claim 4 wherein the control means
comprises a plug for closing the aperture.
9. A silencer according to claim 1 wherein the control means is
provided adjacent an internal surface of the silencer.
10. A silencer according to claim 1 wherein the control means is
provided adjacent an external surface of the silencer.
11. A silencer according to claim 7 wherein the bi-metallic strip
is held at one end such that a free end of the bi-metallic strip is
movable by varying the temperature of the bi-metallic strip.
12. A silencer according to claim 11 wherein the bi-metallic strip
is substantially straight.
13. A silencer according to claim 11 wherein the bi-metallic strip
is arched.
14. A silencer according to claim 7 further comprising a second
bi-metallic strip.
15. A silencer according to claim 14 wherein the second bi-metallic
strip is attached to the first bi-metallic strip at least one
point.
16. A silencer according to claim 14 wherein at least one
temperature the second hi-metallic strip is tensioned against the
first bi-metallic strip.
17. A silencer according to claim 7 wherein the bi-metallic strip
is held in at least two locations such that the bi-metallic strip
may arch.
18. A silencer according to claim 17 wherein the control means is
arranged such that when the bi-metallic strip is at a first
temperature, the bi-metallic strip is substantially flat causing
the fluid outlet to be closed and when the bi-metallic strip is at
a second temperature the bi-metallic strip is arched causing the
fluid outlet to be opened.
19. A silencer according to claim 18 wherein the first temperature
is higher than the second temperature.
20. A silencer according to claim 18 wherein the second temperature
is higher than the first temperature.
21. A silencer according to any preceding claim 1 comprising a
cover to protect the control means.
22. A silencer according to claim 21 wherein the cover comprises a
bi-metallic cover strip.
23. A silencer according to claim 22 arranged such that the
bi-metallic cover strip adopts a flatter configuration when the
fluid outlet is closed and a more arched configuration when the
fluid outlet is open.
24. A method of adapting a silencer for an exhaust system,
comprising the steps of: providing the silencer with a fluid
outlet; and providing silencer control means for opening and
closing the fluid outlet.
25. A method according to claim 24 further comprising the step of
arranging the control means such that when the exhaust system is in
use, the fluid outlet is opened by the control means and when the
exhaust system is idle, the fluid outlet is closed by the control
means.
26. A method according to claim 24 further comprising the step of
arranging the control means such that when the exhaust system is in
use, the fluid outlet is closed by the control means and when the
exhaust system is idle, the fluid outlet is opened by the control
means.
27. A method according to claim 24 wherein the step of providing
the silencer with a fluid outlet comprises the step of forming an
aperture in the casing of the silencer.
28. A method according to claim 24 wherein the step of providing
the silencer with a fluid outlet comprises the step of inserting a
self-tapping plug.
29. A method according to claim 24 wherein the step of providing
the silencer with control means comprises the step of providing
temperature dependent control means arranged to open and close the
fluid outlet in dependence on the temperature of the silencer.
30. A method according to claim 29 wherein the temperature
dependent control means comprises a bi-metallic strip.
31. A method according to claim 27 wherein the control means
comprises a plug for closing the aperture.
32. A method according to claim 24 comprising the step of providing
the control means adjacent an internal surface of the silencer.
33. A method according to claim 24 wherein including the step of
providing control means adjacent an external surface of the
silencer.
34. A method according to claim 30 wherein the bi-metallic strip is
held at one end such that a free end of the bi-metallic strip is
movable by varying the temperature of the bi-metallic strip.
35. A method according to claim 34 wherein the step of providing a
bi-metallic strip is the step of providing a substantially straight
bi-metallic strip.
36. A method according to claim 34 wherein the step of providing a
bi-metallic strip is the step of providing an arched bi-metallic
strip.
37. A silencer according to claim 30 further comprising the step of
providing a second bi-metallic strip.
38. A method according to claim 37 comprising the step of attaching
the second bi-metallic strip to the first bi-metallic strip at
least one point.
39. A method according to claim 37 comprising the step of
tensioning the second bi-metallic strip against the first.
40. A method according to claim 30 wherein the bi-metallic strip is
held in at least two locations such that the bi-metallic strip may
arch.
41. A method according to claim 40 comprising the step of arranging
the control means such that when the bi-metallic strip is at a
first temperature, the bi-metallic strip is substantially flat
causing the fluid outlet to be closed and when the bi-metallic
strip is at a second temperature the bi-metallic strip is arched
causing the fluid outlet to be opened.
42. A method according to claim 41 wherein the first temperature is
higher than the second temperature.
43. A method according to claim 41 wherein the second temperature
is higher than the first temperature.
44. A method according to claim 24 comprising the step of providing
a cover to protect the control means.
45. A method according to claim 44 wherein the step of providing a
cover comprises the step of providing a bi-metallic cover
strip.
46. A method according to claim 45 comprising the step of arranging
the silencer such that the bi-metallic strip cover adopts a flatter
configuration when the fluid outlet is closed and a more arched
configuration when the fluid outlet is open.
47. A silencer for an exhaust system comprising a fluid outlet and
a control for opening and closing the fluid outlet.
48. A method for adapting a silencer for an exhaust system,
comprising the steps of: providing the silencer with a fluid
outlet; and providing a silencer control for opening and closing
the fluid outlet.
Description
[0001] The present invention relates to silencers for exhaust
systems.
[0002] Modern vehicles are often provided with silencers connected
to their exhaust systems in order to reduce noise pollution into
the surrounding environment. When an engine of a vehicle is
running, hot gases pass through the exhaust system. These gases
have a tendency to condense on the internal surfaces of the exhaust
system resulting in fluids, particularly water, collecting in the
exhaust system and running into the silencer.
[0003] Collection of water is undesirable as it tends to cause the
silencer unit to rust, greatly reducing the lifetime of the
silencer unit.
[0004] One solution to this problem is to provide a hole in the
silencer through which fluid may escape. However, puncturing the
silencer unit casing reduces the effectiveness of the silencer and
can cause pollution problems.
[0005] It is an object of the present invention to alleviate
problems associated with previous silencers.
[0006] According to a first aspect of the present invention there
is provided a silencer for an exhaust system comprising a fluid
outlet and control means for opening and closing the fluid
outlet.
[0007] By opening and closing the fluid outlet, the build up of
fluids in the silencer may be controlled.
[0008] In some embodiments of the present invention, the silencer
is arranged such that the fluid outlet is closed by the control
means when the exhaust system is in use and the fluid outlet is
opened by the control means when the exhaust system is idle.
[0009] Such embodiments allow fluids to drain from the silencer
when the exhaust system is idle, preventing build up of fluids in
the silencer, but close the fluid outlet when the exhaust system is
in use, allowing the performance of the silencer to be
improved.
[0010] In other embodiments of the present invention, the silencer
is arranged such that the fluid outlet is opened by the control
means when the exhaust system is in use and the fluid outlet is
closed by the control means when the exhaust system is idle.
[0011] Such embodiments allow fluids to drain from the silencer
when the exhaust system is in use and may prevent the build up of
oily deposits beneath the exhaust system when the system is
idle.
[0012] The fluid outlet may comprise an aperture formed in the
casing of the silencer. The aperture may act as a fluid outlet
directly or may serve to house an outlet portion for conducting
fluid from one side of the silencer casing to the other. In
preferred embodiments, the outlet portion comprises a self tapping
plug. A self tapping plug provides a convenient way of mounting an
outlet portion in the silencer casing. The self tapping plug may
form a drainage aperture.
[0013] When the exhaust system is in use, hot fumes pass through
the silencer, heating the silencer. However, when the system is
idle, the silencer is no longer heated by fumes and the silencer
cools. The control means may comprise temperature dependent control
means arranged to open and close the fluid outlet depending on the
temperature of the silencer. In this way, the fluid outlet may be
opened and closed in dependence on activity of the exhaust
system.
[0014] The temperature dependent control means may comprise a
bi-metallic strip. The control means may comprise a plug mounted on
the bi-metallic strip for closing the fluid outlet.
[0015] The control means may be provided adjacent a surface of the
casing of the silencer. In some embodiments the control means is
provided adjacent an internal surface of the silencer casing. In
such embodiments the control means is conveniently protected by the
silencer casing.
[0016] In other embodiments the control means is provided adjacent
an external surface of the silencer casing. This arrangement is
particularly convenient where the control means is retrofitted onto
an existing silencer.
[0017] Where the control means comprises a bi-metallic strip, the
bi-metallic strip may be held at one end such that a free end of
the bi-metallic strip is movable by varying the temperature of the
bi-metallic strip. In such embodiments the bi-metallic strip may
act like a tongue, moving up and down to open and close the fluid
outlet. A plug for closing the fluid outlet may be provided at the
free end of the bi-metallic strip.
[0018] Where the bi-metallic strip acts in the tongue-like manner
described above, the control means may be arranged such that when
the bi-metallic strip is at a first temperature the bi-metallic
lies substantially flat causing the fluid outlet to be closed and
when the bi-metallic strip is at a second temperature the
bi-metallic strip bends causing the fluid outlet to be open. The
first temperature may be higher than the second temperature.
Alternatively the second temperature may be higher than the first
temperature.
[0019] In other embodiments, in which the bi-metallic strip acts in
a tongue-like manner, the control means may be arranged such that
at a first temperature the bi-metallic strip is arched such that a
portion of the control means closes the fluid outlet and at a
second temperature the bi-metallic strip has deformed causing the
fluid outlet to be opened. The first temperature may be higher than
the second temperature. Alternatively the second temperature may be
higher than the first temperature. In some silencers the use of an
arched bi-metallic strip reduces the risk that material, which may
accumulate around the bi-metallic strip inhibits closing of the
fluid outlet. The use of an arched bi-metallic strip also tends to
increase the rigidity of the bi-metallic strip.
[0020] The control means may comprise a second bi-metallic strip.
The use of two bi-metallic strips allows construction of a harder
wearing and/or more sensitive control means.
[0021] The first and second bi-metallic strips may be arranged to
co-operate to open and close the fluid outlet in dependence on the
surrounding temperature. The first bi-metallic strip may be held at
one end such that another free end of the bi-metallic strip is
movable by varying the surrounding temperature. The second
bi-metallic strip may be held at one end and may extend to contact
the first bi-metallic strip. At least one temperature the second
bi-metallic strip may be tensioned against the first bi-metallic
strip. The second bi-metallic strip may be arranged so as to be
tensioned against the first bi-metallic strip to assist closing of
the fluid outlet at a first temperature. The first and second
bi-metallic strips may be arranged such that at a second
temperature the first bi-metallic strip is caused to open the fluid
outlet. The second bi-metallic strip may be attached to the first
bi-metallic strip at least one point, for example, by spot
welding.
[0022] In other embodiments, the bi-metallic strip may be held in
at least two locations. The bi-metallic strip may be held so that
it can arch between the locations. In such embodiments, a plug for
closing the fluid outlet may be provided on the bi-metallic strip
between the two locations at which the strip is held. The control
means may be arranged such that when the bi-metallic strip is at a
first temperature, the bi-metallic strip is substantially flat
causing the fluid outlet to be closed and when the bi-metallic
strip is at a second temperature the bi-metallic strip is arched
causing the fluid outlet to be opened. The first temperature may be
higher than the second temperature. Alternatively the second
temperature may be higher than the first temperature.
[0023] The silencer may comprise a cover to protect the control
means. Provision of a cover is particularly preferable when the
control means is provided adjacent an external surface of the
silencer casing as such a casing may serve to protect the control
means from the elements. The casing may comprise a bi-metallic
cover strip. In preferred silencers a bi-metallic cover strip forms
an arch over the control means. The cover strip may be arranged
such that it adopts a flatter configuration when the fluid outlet
is closed and adopts a more arched configuration when the fluid
outlet is open.
[0024] According to a second aspect of the present invention there
is provided a method of adapting a silencer for an exhaust system,
comprising the steps of:
[0025] providing the silencer with a fluid outlet; and
[0026] providing silencer control means for opening and closing the
fluid outlet.
[0027] The method may further comprise the step of providing one or
more of the optional features described with respect to the first
aspect of the present invention.
[0028] The method may be a method of adapting a silencer for a
vehicle exhaust system.
[0029] Silencers embodying the present invention will now be
described, by way of example only, with reference to the
accompanying figures in which:
[0030] FIG. 1 shows a silencer fitted to an exhaust system, when
the exhaust system is in use;
[0031] FIG. 2 shows the silencer shown in FIG. 1 when the exhaust
system is idle;
[0032] FIG. 3 shows a second silencer fitted to an exhaust system,
when the exhaust system is in use;
[0033] FIG. 4 shows the second silencer when the exhaust system is
idle;
[0034] FIG. 5 shows a third silencer fitted to an exhaust system,
when the exhaust system is idle;
[0035] FIG. 6 shows the third silencer when the exhaust system is
in use;
[0036] FIG. 7 shows a fourth silencer fitted to an exhaust system,
when the exhaust system is in use;
[0037] FIG. 8 shows the fourth silencer when the exhaust system is
idle;
[0038] FIG. 9 shows a fifth silencer fitted to an exhaust system,
when the exhaust system is in use;
[0039] FIG. 10 shows the fifth silencer when the exhaust system is
idle;
[0040] FIG. 11 shows a sixth silencer fitted to an exhaust system,
when the exhaust system is in use;
[0041] FIG. 12 shows the sixth silencer when the exhaust system is
idle;
[0042] FIG. 13 shows a seventh silencer fitted to an exhaust
system, when the exhaust system is idle;
[0043] FIG. 14 shows the seventh silencer fitted to an exhaust
system when the exhaust system is in use;
[0044] FIG. 15 shows an eighth silencer fitted to an exhaust
system, when the exhaust system is idle;
[0045] FIG. 16 shows a section of bi-metallic strip with a fixing
hole.
[0046] FIG. 1 shows a silencer 1 comprising silencer casing 11, an
exhaust inlet 12 and an exhaust outlet 13. The exhaust inlet 12 and
exhaust outlet 13 are connected to an exhaust system (not shown).
FIG. 1 shows the silencer 1 fitted to an exhaust system when the
exhaust system is in use. In this configuration, a lower portion of
the silencer casing 11 has an aperture 14. Typically the aperture
has a diameter of approximately 0.6 cm (1/4 inch).
[0047] On the external surface of the silencer casing 11 is
provided control means in the form of a substantially straight
bi-metallic strip 2 and a rivet stopper 22. One end of the
bi-metallic strip 2 is attached by a screw 21 to the external
surface of the silencer casing 11. The other end of the bi-metallic
strip is a free end. At the free end of the bi-metallic strip 2 is
provided the rivet stopper 22. The bi-metallic strip 2 is arranged
on the external surface of the silencer casing 11 so that the rivet
stopper 22 is aligned with the aperture 14 in the silencer casing
1. The free end of the bi-metallic strip 2 may move up and down as
the temperature of the silencer varies. In this way the bi-metallic
strip 2 may be considered to act like a tongue for opening and
closing the aperture 14.
[0048] An external cover 3 is provided surrounding the bi-metallic
strip 2 and attached at its periphery to the external surface of
the silencer casing 11. The external cover 3 has a drainage hole 31
on a lower surface of the external cover 3 near to the aperture
14.
[0049] When the exhaust system is in use hot fumes pass through the
exhaust system and through the silencer 1. As the fumes pass
through the exhaust system and the silencer 1 there is a tendency
for fluids to condense on the internal surfaces of the exhaust
system and the silencer 1. These fluids can accumulate in the
silencer 1.
[0050] FIG. 2 shows the silencer 1 when the exhaust system is idle
and the silencer 1 is cool. At this temperature, the bi-metallic
strip 2 is curved and bends away from the external surface of the
silencer casing 11. The rivet stopper 22 provided at one end of the
bi-metallic strip 2 is held a short distance from the aperture 14.
Any fluid which may be present in the silencer 1 may drain through
the aperture 14, past the bi-metallic strip 2 and through the
drainage hole 31 in the external cover 3.
[0051] When the exhaust system is in use hot fumes pass through the
silencer 1 heating the casing of the silencer 11 and the
bi-metallic strip 2. As the bi-metallic strip 2 is heated, the
bi-metallic strip straightens out moving the rivet stopper 22 into
the aperture 14. When the silencer 1 reaches its normal operating
temperature the rivet stopper 22 has moved close to the aperture
14. In this configuration, fluids may accumulate in the silencer 1,
though this tendency is reduced by the increased temperature of the
silencer casing 11. The sealing of the aperture 14 by the rivet
stopper 22 allows the silencer 1 to run quietly.
[0052] The silencer 1 may be formed from a conventional silencer
unit. In order to adapt a conventional silencer unit having a
silencer casing 11, an aperture 14 is drilled in the silencer
casing 11. A second, guide, hole may be drilled in the silencer
casing 11 at a desired location to receive a screw 21. To complete
the adaption of the conventional silencer, a bi-metallic strip 2
having a rivet stopper 22 disposed at one end is attached to the
silencer casing 11 by a screw 21 passing through the other end of
the bi-metallic strip 2. The screw 21 is screwed into the guide
hole, the position of the guide hole having been selected such that
when a bi-metallic strip 2 is fitted the rivet stopper 22 will
align with the aperture 14.
[0053] Optionally an external cover 3 may be provided to protect
the bi-metallic strip 2.
[0054] FIG. 3 shows a second silencer, which is the same as that
shown in FIGS. 1 and 2 except that the bi-metallic strip 2 is
attached by the screw 21 to the internal surface rather than the
external surface of the silencer casing 11. The same reference
numerals are used throughout the Figures to indicate corresponding
parts. Because the bi-metallic strip is now provided on the inside
of the silencer casing 11, an external cover 3 is no longer
provided as the bi-metallic strip is adequately protected by the
silencer casing 11.
[0055] The operation of the second silencer 4 is similar to that of
the silencer 1. FIG. 4 shows the second silencer when the exhaust
system is idle and the silencer 4 is cool. The bi-metallic strip is
cool and curves away from the internal surface of the silencer
casing 11 and the rivet stopper 22 is displaced from the aperture
14. When the exhaust system is in use, as shown in FIG. 3, the
bi-metallic strip 2 is heated by fumes from the exhaust system.
When heated the bi-metallic strip straightens moving the rivet
stopper 22 to cover the aperture 14.
[0056] Any fluid accumulated in the second silencer 4 may escape
via the uncovered aperture 14 when the exhaust system is idle and
the silencer is cool. However, when the exhaust system is in
operation, the aperture 14 is covered by the rivet stopper 22,
enhancing the quietening effect of the silencer.
[0057] FIGS. 5 and 6 show a third silencer 1 attached to an exhaust
system. The third silencer is similar to the second silencer in
that it comprises control means in the form of a bi-metallic strip
2 and a rivet stopper 22. As before the bi-metallic strip 2 is
attached to an internal surface of the silencer casing 11. However,
the third silencer differs from the second silencer in two
respects. In the third silencer, the bi-metallic strip 2 is arched
rather than being substantially straight. This change is a matter
of construction of the bi-metallic strip 2 and tends to prevent
material which may collect between the bi-metallic strip 2 and the
internal surface of the casing 11 from preventing the bi-metallic
strip 2 closing the aperture 14 properly. As the temperature of the
bi-metallic strip is varied the strip deforms causing the arched
portion to pivot away from the screw.
[0058] Further, operation of the third silencer differs from that
described with respect to the first and second silencers. When the
exhaust system is in use, the arched bi-metallic strip 2 is warmed
by exhaust fumes. This causes the arched portion to raise adopting
the configuration shown in FIG. 6. In this configuration the rivet
stopper 22 is held away from the aperture 14 and any fluids which
condense in the silencer may escape through the aperture 14. On the
other hand, when the exhaust system is idle, the bi-metallic strip
cools and the arched portion of the bi-metallic strip 2 lowers,
adopting the configuration shown in FIG. 5. In this configuration,
the rivet stopper 22 is held over the aperture 14 and fluids may
not escape. The retention of fluids within the silencer 1 tends to
reduce the build up of oily deposits below the silencer, which may
be of concern if the silencer is mounted on a vehicle.
[0059] FIGS. 7 and 8 show a fourth silencer 1 attached to vehicle
exhaust system.
[0060] In contrast to the tongue-like arrangement of the
bi-metallic strip 2 in the previously described embodiments the
bi-metallic strip of the fourth silencer is held between two screws
21. One screw 21 is provided either side of an aperture 14 in the
casing 11 of the fourth silencer 1. Either end of the substantially
straight bi-metallic strip 2 is attached to a respective screw 21
via an elongate fixing hole provided in the bi-metallic strip 2.
FIG. 16 shows a section of bi-metallic strip provided with such
fixing holes. A rivet stopper 22 is provided substantially at the
mid-point of the bi-metallic strip 2 and aligned with the aperture
14. When the exhaust system is in use the bi-metallic strip 2 is
warmed by exhaust fumes and tends to straighten to lie flat against
the silencer casing 11. This configuration is shown in FIG. 7 and
causes the rivet stopper 22 to close the aperture 14 preventing
fluid from escaping from within the silencer. When the exhaust
system is idle the bi-metallic strip 2 tends to cool causing the
bi-metallic strip to arch between the two screws 21 and moving the
rivet stopper 22 away from the aperture 14. This configuration is
shown in FIG. 8: In this figure the aperture 14 is open and fluids
may escape from the silencer 1.
[0061] FIGS. 9 and 10 show a fifth silencer fitted to an exhaust
system. The silencer casing 11 shown in these Figures is of the
type previously described, however, the thickness of the silencer
casing 11 adjacent the control means is shown in these Figures for
the purposes of clearer illustration. Adjacent the silencer casing
11 is provided a fixing plate 6. In the embodiments shown in FIGS.
9 and 10, the aperture 14 described with reference to the previous
embodiments, has been replaced by a self-tapping fixing plug 5.
This fixing plug 5 is provided with a drainage hole (not shown) and
allows fluid to pass from inside the silencer 1 to the outside. As
may be seen in the Figures, the self-tapping fixing plug 5 forms an
aperture in both the fixing plate 6 and the silencer casing 11.
[0062] A fixing plug 5 may be used in place of the aperture 14 in
any of the described embodiments. In order to fit a fixing plug, a
fixing plate 16 is provided adjacent the silencer casing and the
self-tapping fixing plug 5 is inserted. The provision of the fixing
plate 6 ensures that there is sufficient thickness of metal or
other material for the fixing plug 5 to secure itself to. The use
of the self-tapping fixing plug 5 and fixing plate 6 is
particularly preferable when retrofitting existing silencer
units.
[0063] In the embodiment shown in FIGS. 9 and 10, the control means
is provided on an external surface of the silencer casing 11, which
would be typical for a retro-fitting operation. A bi-metallic strip
2 is attached to the external surface of the fixing plate 6 by a
screw 21 and a rivet stopper 22 is provided at a free end of the
bi-metallic strip 2 to form a tongue-like arrangement of the type
previously described. The rivet stopper 22 is aligned with the
fixing plug 5. Also provided is a bi-metallic strip cover 4. This
bi-metallic strip cover 4 is made of a non-corrosive material and
is arranged to cover the control means and to protect it from the
elements.
[0064] In use, the bi-metallic strip 2 and the rivet stopper 22 act
in a tongue-like fashion to open the fixing plug 5 when the exhaust
system is in use and to close the fixing plug 5 when the exhaust
system is idle. The bi-metallic strip cover 4 serves to cover the
control means. When the exhaust system is in use, the silencer is
warmed and the bi-metallic strip 2 and rivet stopper 22 tend to
cover the fixing plug 5. In this situation the bi-metallic strip
cover 4 tends also to be warmed and to straighten, lying nearly
flat across the top of the control means. The silencer 1 therefore
tends to adopt the configuration shown in FIG. 9. When the exhaust
system is idle the bi-metallic strip 2 tends to cool holding the
rivet stopper 22 away from the fixing plug 5. At the same time the
bi-metallic strip cover 4 also tends to cool, arching and providing
room for the bi-metallic strip 2 which now curves away from the
silencer casing 11 and fixing plate 6. Thus the bi-metallic strip
cover 4 closely follows the changing size of the control means and
provides protection against damage.
[0065] FIGS. 11 and 12 show a sixth silencer fitted to an exhaust
system. The sixth silencer is very similar to the fifth silencer
except that the tongue-like configuration of the bi-metallic strip
2 in the fifth silencer has been replaced by a bi-metallic strip 2
provided between two screws 21 which acts in a similar manner to
that described in respect of the fourth silencer.
[0066] Adjacent an external surface of the silencer casing 11 of
the sixth silencer is provided a fixing plate 6. A self-tapping
fixing plug 5 forms an aperture in the silencer casing 11 and
fixing plate 6 and serves to provide a fluid outlet. Outside the
fixing plate 6 and attached between two screws 21 is provided a
bi-metallic strip 2. Attached to the bi-metallic strip 2, roughly
at its mid-point, is a rivet stopper 22 for covering and uncovering
the fixing plug 5. Covering the control means is a bi-metallic
strip cover 4.
[0067] When the qxhaust system is in use the bi-metallic strip 2
tends to straighten lying adjacent the fixing plate 6 and causing
the rivet stopper 22 to cover the fixing plug 5 preventing escape
of fluid from the silencer 1. When the exhaust system is in use the
silencer 1 tends to warm the bi-metallic strip cover 4 causing this
to straighten and lie close to the bi-metallic strip 2.
[0068] When the exhaust system is idle both the bi-metallic strip 2
and the bi-metallic strip cover 4 tend to cool The bi-metallic
strip 2 tends to arch between the two screws 21 moving the rivet
stopper 22 away from the self-tapping fixing plug 5 and allowing
fluid to escape from within the silencer 1. At the same time the
bi-metallic strip cover 4 tends to cool arching between the two
screws 21 and allowing space for the arching bi-metallic strip 2.
The bi-metallic strip cover 4 therefore provides close protection
for the bi-metallic strip 2 whilst allowing space for the
bi-metallic strip 2 to arch.
[0069] FIGS. 13 and 14 show a seventh silencer fitted to an exhaust
system. The seventh silencer is similar to the second silencer
except that the single bi-metallic strip 2 in the second silencer
has been replaced by a substantially straight primary bi-metallic
strip 80 and an arched secondary bi-metallic strip 81 in the
seventh silencer. Both the primary bi-metallic strip 80 and the
secondary bi-metallic strip 81 are fixed to the silencer casing 11
by a screw 21. Attached to the primary bi-metallic strip 80 is a
rivet stopper 22 aligned with an aperture 14 in the casing 11. The
primary bi-metallic strip 80 is movable up and down in a
tongue-like fashion to cause the rivet stopper 22 to cover and
uncover the aperture 14 in dependence on the temperature of the
silencer 1. The secondary bi-metallic strip 81 is provided arched
over the top of the primary bi-metallic strip 80 and in contact
therewith near the screw 21 and at a point part way along the
length of the primary bi-metallic strip.
[0070] In this embodiment, the secondary bi-metallic strip 81 is
arranged on top of the primary bi-metallic strip 80. When the
control means is in the configuration shown in FIG. 13 the
secondary bi-metallic strip 81 is secured by the screw 21 such that
it is tensioned against the primary bi-metallic strip 80. The
tension in the secondary bi-metallic strip 80 tends to hold the
primary bi-metallic strip 81 against the interior surface of the
silencer casing 11 keeping the aperture 14 closed.
[0071] In use the silencer tends to warm up. As the secondary
bi-metallic strip 80 warms, it deforms, easing the force it applies
to the primary bi-metallic strip 81. The primary bi-metallic strip
also warms and deforms causing the rivet stopper 22 to move away
from the aperture 14.
[0072] This type of silencer arrangement is particularly
advantageous if the silencer only experiences a small temperature
change during normal operation. In such cases, in order to increase
the sensitivity of the primary bi-metallic strop, to changes in
temperature, the primary bi-metallic strip is made longer and
thinner. This reduces the strength of the primary bi-metallic
strip. Provision of the secondary bi-metallic strip in this
situation tends to improve the strength of the bi-metallic strip
arrangement.
[0073] The secondary bi-metallic strip 81 may be provided alongside
the primary bi-metallic strip 80 and in contact therewith. In the
embodiment shown, the secondary bi-metallic strip 8 1 is only
attached to the primary bi-metallic strip 80 by the screw 21. The
other end of the secondary bi-metallic strip 81, opposite the screw
21, is in contact with the primary bi-metallic strip 80 but is free
to move relative thereto. In other embodiments the secondary
bi-metallic strip 81 may be attached to the primary bi-metallic
strip 80. For example, the secondary bi-metallic strip 81 may be
spot welded to the primary bi-metallic strip 80.
[0074] In the seventh silencer the primary bi-metallic strip 80 is
provided adjacent the silencer casing 11 on the interior of the
silencer 1 and the secondary bi-metallic strip 81 is provided on
top of the primary bi-metallic strip 80. In an alternative
silencer, shown in FIG. 15, a substantially straight secondary
bi-metallic strip 81 is provided between the silencer casing 11 and
an arched primary bi-metallic strip 80. In this case when the
silencer is idle the secondary bi-metallic strip 81 is curved and
tends to hold the primary bi-metallic strip 80 away from the
interior surface of the silencer casing, keeping the aperture 14
open.
[0075] As the temperature of the silencer increases the secondary
bi-metallic strip 81 tends to straighten allowing the primary
bi-metallic strip 80 to move towards the interior surface of the
silencer casing 11, closing the aperture 14.
[0076] Silencers have been described in which the aperture or
fixing plug are opened and closed in dependence on the temperature
of the silencer 1. In each of the embodiments described whether the
aperture or fixing plug is covered or uncovered when the exhaust
system is idle could be altered by modification of the design.
Therefore, whilst the embodiments above describe particular modes
of operation, it should be appreciated that modifying these
embodiments to include or exclude optional features of the present
invention is a straight-forward matter.
* * * * *