Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to exhaust silencer casings.
Such silencer casings contain packing in order to assist
in silencing exhaust gases from an engine by virtue of conversion
of kinetic energy of the exhaust gases lnto mechanical
displacements of the packing and thus heating thereoE.
The packing may be Eibre "Eluffed-up" into a wool-like
consistency. This material can be produced by chopping conkinuous
strands of glass fibre.
In the past such silencer casings have been packed
manually and, to assist in this process, it has been proposed to
apply a vacuum to one end of the silencer casing.
In order to adapt the process for automatic operation
glass fibre material in wool-like form has been Eed into a hopper,
from which it passes along ducts before being metered into
individual quantities, each suitable for packing one silencer
casing~ However, the material has been prone to clog in the ducts
and this has made the accurate metering of the material difficult,
if the expense of weigh pans is to be avoided.
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The present invention provides a method of packing an
exhaus~ silencer casing comprising establishing gas flow through
the casing, chopping into discrete lengths a strand consisting o
mineral fibres, and allowing the chopped fibres to be carried in
the gas flow through a restriction, the breadth of which is less
than one inch (25.~mm) to "fluff-up" the fibres into a wool-like
material passing into the casing.
The e~haust silencer casing is packed by establishing
gas flow through the casing, chopping into discrete lengths a
strand consisting oE mineral fibres, and allowing the chopped
fibres to be carried in the gas 1OW through a restriction, the
breadth of which is less than one inch (25.4 mm) to "Eluff-up" the
fibres into a wool-like material passing into the casing.
It should be noted that the term 'Istrand'l used in this
speciEication refers to a plurality of fibres which may be
twisted, plaited or laid parallel. A strand typically comprises
200 - 1600 fibres. The term l'rovingl' refers to a bundle of
stands. A roving typically comprises eight or more strands and
may comprise over 500 fibres. The term "fibrell refers -to an
elonga-te object, such as a filament, Erom which a wool-]ike
material can be made.
It has been found that the individual fibres of each
discrete length of chopped strand separate as they are carried
into the silencer casing in the gas flow so tha~ the fibres
IlEluff-upll in the desired manner in the silencer casing itself or
as they enter the casing.
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This invention will now be illustrated, merely by way of
example, with reerence to the accompanying drawings, in which:
Figure 1 is part sectional view of a first embodiment of
apparatus according to this invention;
Figure 2 is a side view of a gun of the apparatus shown
in Figure l;
Figure 3 is a front view of the gun shown in Figure 2;
-- 4 --
Figure 4 i9 a plan view of the gun shown in Figure 2; and
FLgure 5 i~ a schematic view of a second embodiment of
apparatus accordlng to this lnvention.
The apparatuq for paeking a silencer casing 1 shown in
Figure 1 eomprises vaeuum produeing apparatus 2, sealing
apparatus 3 and a gun 4.
The sileneer casing 1 i9 circular in eross-section, and
one end thereof is elosed by an end piece 5 whic.
supports a per?orated tube 6 extending througn the
silencer easing 1. The end piece 5 also supports a stu~
pipe 7 which, in use, eonnects the sileneer to the rest
of the exhaust assemDly. A similar end pieee (not shown)
bearing a stub pipe is welded to the other end of the
silencer casing 1 after it has been packed.
The vacuum producing apparatus 2 has a rubber sealing
member 3 which fits tightly around the stub pipa 7. A
vaeuum is produced in the apparatus by means of a
centr;Lugai compres~or (~ot qhown) driven by a ~orty
horse power (29.8 KW) motor (not shown). This produce~ a
vacuum of around ten inehes of mereury (33.~ ~Nm 2) in
the apparatus 2.
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- 5 - 22870-91
The sealing apparatus 3 likewise has a sealing member 9
and this seals against the open end o-E the casing 1 and also
blocks oEf the open end of the perEorated tube 6, as the tube 6
should not be filled with any packing material. The sealing
member 9 includes a circular aperture 10 whose diameter is 3/4
inch tl9mm) ~hich provides communication between the interior oE
the sealing apparatus 3 and the interior of the casing 1. The
aperture 10 forms a restriction in the pathway from the gun 4 to
the interior of the casing 1.
Figure 2 shows roving being fed into the gun 4 and
discrete lengths of this being emitted from the gun 4. The roving
consists of a bundle of strands each of which consists of a
plurality of Eibres, e.gc at least 100 or at least 1000 fibres, oE
a mineral such as basalt, i.e. the material from which rockwool is
made. Other types of Eibres which when "fluffed-up" Eorm a wool-
like material may be used, for instance ceramic fihres. The
fibres typically have a diameter in the range of 6-12 microns.
Attention is drawn to our Canadian Patent No. 1,240,131 which
relates specifically to the use of continuous glass fibres in
similar apparatus. The fibres in each strand may be twisted,
plaited or laid parallel and the Eibres
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may be continuoua,ie extend the length of ~he 3trand, or
may be relatively ~hort ln which cage they may be spun to
form a strand in much the same manner as cotton or wool
i~ ~pun to form threads. Preferably, the rovlng fed into
the gun 4 comprise3 eight or more strand~ 90 that each
discrete chopped len~th thereof conslsts of a large
number of fibres, eg over 2000 fibre3. However, lt is
possible to operate the apparatu~ with only a ,~ingle
strand being fed into the gun 4. Preferably, the fibres
have a diameter of les~ than 30 micron~ or leqs than 15
micron~. The roving iQ fed into the gun 4 from a 3pool
(not ~hown) containing a length of about two hundred
meters of roving.
The gun 4 has an air-powered motor, contained in a
housing 11, to which a rubber roller 12 is coaxially
attached. The roving is, driven through the gun 4 by
means of the rubber roller 12 and a steel roller 13 which
i~ hard in contact with the rubber roller 12. The roving
i~ cut into discrete lengths by means of a cutter 14
mounted diametrically through a further roller 15 so that
the cutter ]4 extends along a generator of ~he "oller
15. Every half revolution of roller 15, the rovln6 i3
severed at the point of contact between the roller~ 12
and 15. The roll0rs 12, 13 and 15 are contalned in a
hou~ing 16 (see Figures 3 and 4) havlng an inlet 17 and
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an outlet 18. Exhau3t air from the air powered motor is
~ed into the housing 16 and, since the area of the outlet
18 i~7 much greater than that of the inlet 17, the chopped
lengths of roving are proJected out of the gun 4 with the
aid of a blast of this exhaust air.
In operation a silencer ca3ing 1 to be fllled wlth
packing is fittsd onto the vacuum producing apparatus 2
and the sealirg apparatus 3 i3 brought up to the open end
of the casing 1. The centrifugal compressor i3 ~tarted.
The gun 4 is then run and left running for a
pre-determined period of time. This pre-deter~ined
period corresponds to the desired weight o~' fibre it is
desired to pack into the particular silencer casing 1 ,
and this can be calculated simply from the weight per
i5 unit len~th of the roving and the velocity at which the
roving i~7 fed through the sun 4.
The chopped lengths of roving projected from the gun 4
are all sucked through the aperture 1~ in the sealing
member 9 by the vacuum applied at the other end of the
silencer ~asin~7 1, and the caslr:g 1 i9 ~7radually filled
with fibre~. It ha~7 been found that the ~ibres in each
chopped length of roving 3eparate either before they
enter the silencer casing 1 or while ~hey are in the
silencer casing 1 (probacly the 3eparation mainly takes
place within the silencer), and this result3 in the
production o~ the desired wool-like form of the ~ibre~ in
the casing 1. The air flow within the ca3ing 1 will Or
cour~e be turbulent slnce it is being qucked through the
perforated tube 6. The fibres do not pass into the tube
6 themselves.
One advantage of the apparatus and method deqcribed is
tha~ it i3 possible to accurately meter the quantity o f
fibres with which each casing i9 packed. Also, the
ducting require for handling wool-like glass fibre is not
required.
The described method and apparatu3 may be used to pack
any ~orm of silencer casing including those in which
exhaust gases ~ake multiple passes Or the whole or part
of the length Or the silencer casing.
Variouq modifications Or the method or apparatus are of
course possible. For example, test~ have been carried
out with an arcuate aperture 10 in the sealing member 9,
the aperture 10 having length of about four times its
breadth. Although the roving "flufred-up" in a
satiqfactory manner, it wa~ nevertheles~ found that it
_ 9 _
"~luffed-up" better with the 3/4 lnch (19 mm) diameter
aperture referred to earlier.
A second embodiment of the apparatu~ accordlng to this
lnvention i3 shown ln Figure 5. This apparatus di~fers
from that ~hown in the previous figures in that no vacuum
i9 requirecl to draw the chopped roving into the silencer
casing. Instead, the chopped roving is carried into the
casing by an air flow.
A ~ilencer ^asing 20 to be ~illed with packing is closed
a the lower end as seen in Figure 5 by a closing plate 21
~hich ha3 an aperture through wnich a perforated tube 22
of the silencer extends. The silencer casing 20 is
mounted on a plat~orm 23 through which air can pass. At
the upper end of the silencer casing 20 a3 seen in the
l; Figure is a closing plate 24 which carries a plug 25 for
closing the upper end of the perforated tube 22.
Chopped strands Or roving aré fed in~o the silencer
casing 20 via a tube 26 and a conical member 27, the tube
26 being sealed in an aperture in the closing plate 24.
The tube 26 thus forms a restriction in the pathway from
a gun 28 to the interior of the ca~ing 20.
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The gun 28 supplies chopped roving to the wide end of the
conical member 27. The gun 28 i3 similar to the gun 4
described except that the exhaust air thereof does not
assist in projecting the chopped strands of roving rrom
the gun 28, the chopped roving being projected from he
gun 28 solely by the rotation of the rollers 12, 13 and
15.
A narrow tube 2, opens into the tube 26, and compressed
air i~ ~uppl.e~ throu~h the narrow tube 29 into the tuDe
1(~ 26. It has been found that the compressed air fed 1nto
the tube 26 draws large quantities of a1r into the
conical .member 27, through the wide end thereof and hence
through the tube 26 into the silencer casing 20. The
chopped roving is therefore carried by this air flow into
the silencer casing 20. The air rflow leaves the silencer
casing 20 via the perI'orated tube 22. It has been found
that the fibres of the chopped roving ar~ "flu$'$'ed up" in
thi3 proces~, and that the silencer casing 20 is filled
in a very satisfactory manner.
Examples of 3uitable dlmen~ions and pre~sures for the
apparatu3 shown in Figure 5 will now be given.
Length of tube 26 3 inches (76.2 mm)
Dlameter of tube 26 1/2 inch (12.7 mm)
Semi-ansle of conical member 27 30
Diameter of wide end of
j conical member 27 3 inches (76.2 mm)
Angle between tubes 29 and 26 35
.
Pressure or` compressed air in 100 lbs ins
tube 29 (689. 7 KNm
It is believed that the narrow diameter of the tube 26 is
important in "flu~fin~-up" the chopped roving, since only
with a narrow diameter is sufficient turculence created
in the tube 26 to acnieve thio. Similarly, it is
believed that the narrow aperture 10 in the apparatus
shown in Figure 1 is responsible for creating the
necessary turbuLence to cause "fluffing-up". The
narrower the diameter oP the tube 26 or aperture 10, the
smaller the compressed air pressure or vacuum needed to
"fluff-up" the chopped rovlng. However, if the diameter
i9 too ~mall, the restriction is prone to clogging.
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It will be apparent that any means of eqtablishing an air
flow or gas f10w through the sileneer easin~ to be paeked
~ay be used to earry the ehopped roving into the casing.
This invention also relates to an exhaust slleneer casin~
paeked in accordance with the method deseribed above and
to an exhaust system eomprising sueh a silencer easing.
