Note: Descriptions are shown in the official language in which they were submitted.
20549 fit
H?~CT~GRQU~D OF ~.~.i.'~'~'E'.13~.~0:~
The present invention relates t.o mufflers, and
mere particularly, mufflers for vehicular exhaust
systems used with interna:L combusti~un engines and to
methods of fabricating or manufacturing such
mufflers.
Over the years, vehicular exhaust system
mufflers, silencers, resonators and ths~ like
(hereinafter collectively referred to as "mufflers" )
l0 have employed many different designs. Nevertheless,
most mufflers have included one or more end tubes;
one or more flow tubes that may be perforated, in
whole or in part, so as to permit the expansion of
the combustion gases within the muffler; one or more
panels or baffles that are often described as end
panels or internal panels and that among other
things serve to support the tubes; and an inner, and
often an outer sheet metal body wrapper that. serves
as a housing for the other muffler components.
Generally speaking, the fabrication of mufflers in
the past has involved a number of steps, including
the assembly of the reversing unit and end cap sub-
assemblies.
In one muffler design, the reversing unit sub
assembly includes two internal panels and two flow
tubes. The peripheral edge of each internal panel
has an integral flange that projects perpendicularly
from the plane of the panel. Each of the internal
panels also includes one or more apertures, and each
aperture is surrounded by an integral,
perpendicularly projecting flange. The internal
panels are disposed, side by side, so that in
general apertures in the panels are aligned in
pairs.
In fabricating the reversing unit sub-assembly,
the opposite ends of the flow tubes are secured
within aligned apertures by a mechanical lock joint,
such as the mechanical lock joint shown in U.S.
2054962
Patent No. 4,570,747. The inner sheet metal wrapper
is folded or configured into a generally oval shape
so as to define a generally cylindrical volume into
which the reversing unit sub-assembly may be
inserted. The ends of the wrapper are joined
together by seam locking, spot welding, seam welding
or the like. One of the internal panels is inserted
into the inner wrapper first and is called the
leading panel. The internal panel, inserted into
l0 the inner wrapper last, is called the trailing
panel.
At this point in the muffler fabrication, it
has been customary to make a number of spot or tack
welds between the inner wrapper and the peripheral
flange on the trailing panel. These welds attach
the trailing panel to the inner wrapper and thus
locate the entire reversing unit sub-assembly
relative to the inner wrapper.
The next step in the fabrication has been to
apply an outer sheet metal wrapper around the
assembled reversing unit sub-assembly and inner
wrapper. The outer wrapper is shaped or configured
about the inner wrapper such that the respective
side edges of the two wrappers are adjacent. zts
end edges are then seam locked together so as to
hold the outer wrapper tightly in place over and
around the inner wrapper.
Two end cap sub-assemblies are usually required
to complete the f abrication of the muf f ler . Each
's0 end cap sub-asse;rtb3y includes an end pgnel !,suing a
continuous peripheral edge. Each end panel. has at
least one aperture that is surrounded by a
perpendicularly projecting, aperture surrounding
flange. End tubes are disposed, between their ends,
in the end panel apertures and are secured to the
end panels by a mechanical lock joints such as shown
in U.S. Patent No. 4,565,260.
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In the assembled muffler, an end of each end
tube is usually connected with a~ end of a flow
tube. In the past, the connected end of the end
tube is sized so as it can be tightly press fit
within the inside diameter of its associated flow
tube end when the end cap assembly is brought
adjacent to the side edge of the inner arid outer
wrappers. This press fitting requires the
maintenance of close or high tolerances. The
l0 overlapped, interfitted ends of these tubes have
been secured together by a mechanica:~. lock joint
such as shown in U.S. Patent No. 4,570,747. The
press fitting poses no problem with respect to
dislocating the reversing unit sub-assembly,
relative to the inner and outer wrappers be<:ause as
noted, t2~.at sub-assembly is held in place within the
wrappers by the plurality of welds.
After the end tubes have thus been connected
with the flow tubes, the side edges of the wrappers
and the peripheral edges of the end panels ~sre spun
and crimped together. This completes the
fabrication of the muffler.
While the above method of fabricating mufflers
continues to produce a duality muffler product, the
necessity of utili2ing welds to hold the reversing
unit sub-assembly, relative to the inner wrapper, is
a time consuming and thus expensive step.
Additionally such welding can pose potentially
serious health and workplace safety concerns for the
fabrication workers. Besides welding can adversely
affect the integrity of the protective coating
applied to the muffler components, by creating a
site of nucleation of corrosion. This defeats the
purpose of applying the protective coating and of
using mechanical lock joints. Those working in this
art have long sought to eliminate having to weld
during muffler fabrication.
20549fi2
The above-mentioned use of mechanical lock
joints has reduced the use of welding -- and the
resultant disadvantages -- in muffler fabrication.
Nevertheless, to obtain sufficient torsionai
resistance for such a joint, such as, for example,
the joint shown in U.S. Patent No. 4,565,260, a die
has to be used as a backup for the r. atary tool ing
utilized to deform the tube surface into the joint.
Moreover, tooling such as disclosed in U.S. Patent
No. 4,821,391, is required in order to form such
mechanical lock joints an a production line basis.
The cost of such tooling is relatively expensive,
and the formation of the joints, even using such
sophisticated tooling, is relatively time consuming.
i5 Thus, the art has also been seeking improved
mechanical lock joints that can secure against the
torsional and axial forces normally experienced in
mufflers during their assembly and that can be
relatively quickly and inexpensively formed.
SUI~iARY OF THE INVENTION
In its principal aspect, the present invention
eliminates the need for any welding in the
fabrication of vehicular exhaust system mufflers
through the use of a novel approach to assembling
the overlapped ends of the end and flow tubes and
the employment of improved mechanical lock joints.
Not only are these novel mechanical lock joints gas
tight and able to resist the torsional and axial
forces normally experienced by the muffler
components during fabrication of the muffler, but by
reason of their utilization, the muffler can be
fabricated in much less time and at significantly
less cost.
One of these improved mechanical lock joints is
formed between the telescoping, interfitted,
overlapped ends of the flow and end tubes and the
internal panel supporting these tubes. By using
2054902
this improved mechanical lock joint, the overlapping
ends of the Enc. tube and flow tube need not be press
fit together. Rather, the ai~.:e of the' telescoping
end tube end is preselected so that it loosely fats
5 within the end of the flow tube. Consequent:Ly,
there is no possibility that any significant force
will be applied to the reversing sub--assembly unit
during the assembly of the end cap sub-assemblies to
the muffler. This, in turn, obviates the need to
weld or otherwise secure the reversing unit sub-
assembly to the inner wrapper.
The usage of this improved mechanical lock
joint also permits an important easing of the
manufacturing tolerances with respect to the sizing
of the overlapping ends of the end and flaw tubes
and with respect to the axial locations of these
ends relative to each other and to internal panel
aperture flange. Heretofore close tolerances had to
be maintained. This easing of the to7lerances
minimizes the manufacturing time required and
reduces scrap.
The present invention also contemplates the use
of another improved mechanical lock joint, This
novel lock joint is formed between the end tube and
the end panel.
In contrast to lock joints previously utilized
in .the fabrication of mufflers, bath improved
mechanical lock joints of the present invention can
be formed without the use of back-up dies. This
makes the tooling required for forming this joint
significantly less expensive and the fabrication of
the joint much less time consuming as compared to
prior mechanical lock jointer such as shown in U.S.
Patent Nos. 4,565,260 and 4,570,747.
Accordingly, it is a principal object of the
present invention to provide an improved muffler for
a vehicular exhaust system used with an internal
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combustion engine and a:iso to provide an improved
method for fabricating or making such a muffler.
Another object of the present invention is to
provide an improved muffler and muffler fabrication
method, as described, where welding need not be used
in the fabrication ef the muffler arid where the
improved mechanical lock joints utilized to
fabricate the muffler can be readily and relatively
inexpensively formed under relatively relaxed
manufacturing tolerances and by the use of tooling
that does not require the employment of back up
dies. A related object of the present invention is
to provide an improved muffler which employs an
improved mechanical lock joint to attach a tube to
the aperture flange of a panel, where this lock
joint includes a substantially continuous,
circumferential, skewed bead, where the plane of
this bead is disposed at an oblique angle of less
than 90' with respect to the longitudinal axis of
the tube, and where the bead extends from beyond one
side of the panel to beyond the distal end. of the
panel's aperture flange on the other' side of the
panel.
A further object of the present invention is to
provide an improved muffler which employed improved
mechanical lock joints to attach end tubes to the
end panels, where the lock joint includes a series
of spaced apart, circumferential, aligned, elongated
deformations in the overlapped portions of the end
tube and the end panel aperture flange and a
substantially continuous, circumferential bead in
the part of the end tube adjacent to other side
surface of the end panel (that is, the side surface
opposite the panel's aperture flange), where the
plane of these deformations is at an angle of
substantially 90' with respect to the longitudinal
central axis of the end tube, where preferably the
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major axes of these deformations are aligned with
the plane of the defo;-mations, and where the plane
of the circumferenti.al bead is at .gin angle of
substantially 90° with respect tc the longitudinal
axis of the end tube.
Still another object of the present invention
is to provide an improved muffler of the typed
described which includes a wrapper that has been
configured or shaped so that its inner surface
defines a volume, between its side edges, l~.~aving a
predetermined cross-sectional configuration; which
has a first panel having a peripheral edge ge:neral.ly
congruent with the predetermined cross-sectional
configuration so that when the panel is disposed
within the volume, the peripheral flange of the
panel i5 in contact with but is metallurgically
unbonded to the inner surface of the wrapper; where
one tube is disposed, at least in part, within the
volume so that its one end is disposed within and
extends through an aperture in the panel, with the
end of the one tube having a preselected inner
diameter; where another tube extends from without to
within the volume, with the other tube having a
first end that has a preselected outer diameter so
that this end of the other tube fits :Loosely,
telescopically, and overlappingly within the first
end of the one tube so as to minimize the
possibility that the forces applied in assembling
the ends of the tubes will cause axial displacement
of the panel relative to the wrapper and with the
end of the other tube extending within the end of
the one tube to a point beyond the plane of the
panel; and which includes mechanical lock joint for
locking together the overlapped ends of the tubes so
as to maintain the relative axial positions of the
overlapped ends and to resist relative movement
between the overlapped ends due to the application
2054902
3
of torsional and axial for;:es that the t~,xbes
experience during assembly of the muffler. A
related object of the present invention is to
provide an improved muffler of the type described
where the other tube extends through an aperture in
a second panel include:> another mechanical lock
joint for locking the other tube within the second -
panel aperture; and which includes shill~ another
mechanical lock joint for locking the one tube in
the first panel aperturem
A still further object of the present invention
is to provide an improved method of fabricating or
manufacturing a muffler of the type described where
the method includes the steps of placing an end of
the flow tube :into and through an aperture in the
internal panel; mechanically locking this end of the
flow tube in the internal panel aperture; shaping a
sheet metal wrapper into a configuration generally
corresponding to the outer configuration of the
periphery of the internal panel; joining the ends of
the wrapper together; placing the mechanically
locked flow tube and internal panel within the
shaped configuration of the wrapper so that inner
surface of the wrapper is in contact with but is
metallurgically unbonded to the peripheral edge of
the internal panel; placing an end tube within an
aperture in a end panels mechanically locking the
end tube within the end panel aperture; mounting the
mechanically locked end tube and end panel auto the
side of the wrapper so that an end of the end tube
is loosely, telescopically and overlappingly fitted
Within an end of the flow tube so as to minimize the
chances that the farces applied during the mounting
will cause displacement of the internal panel
relative to the wrapper; mechanically locking
together the overlapped ends of the flow and end
tubes so as to maintain the relative axial positions
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of these overlapped ends and to resist relative
movement between the overlapped ends> due to the
application of torsional and axial forcaes that are
experienced by these tubes during the fabrication of
the muffler; and mechanic~ally joining the side edge
of the wrapper and the peripheral edge of the end
panel.
These and ather objects, aspects and advantages
of the present invention are more fully set forth in
the following detailed description of the preferred
embodiment of the present invention, which follows a
brief description of the accompanying drawings.
F3RjEF DESCRIPTION OF TAE DRAWINGS
FIGURE 1 is a cross-sectional view taken along
a vertical plane, including the central longitudinal
axis, of the improved muffler of the present
invention;
FIGURE 2 is a cross-sectional view taken along
the line 2-'? in FIGURE 1;
FIGURE 3 is an enlarged, partial, cross-
sectional view of an end tube disposed within an end
panel aperture prior to the formation of the
mechanical lock that is used to attach. these
components;
FIGURE 4 is an enlarged, partial, cross-
sectional view showing an end of a flaw tube
mechanically locked within an internal panel
aperture:
FIGURE 5 is an enlarged, partial sectional view
showing the mechanical lock joint between the
overlapped ends of the flow and end tubes as well as
the mechanical lock joint used to attach the end
tube to the end panel; and
FIGURE 6 is a cross-sectional view taken along
the line 6-6 in FIGURE 5.
~,~CRIPTTON O~ THE PRA"FERRED EMEODIMENT
Referring now to FIGURE 1, an .improved muffler
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of the presrnt l nve~nti on l s :sho:vn c,~n~ral ly at : ? .
This muffler includes two internal navel or baffles
? 4 and 16, two parti,all;,. perforatec9 flow tubes 18
and 22, two end tunes 24 and ?6, two end panels 28
and 32, an inner sheet metal body wrapper 34, and an
outer sheet rn,etal body wrapper 36. for all intents
and purposes, the structure and function of each of
the two internal panels, the two flow tubes, the two
end tubes, and the two end panels are substantially
1.0 identical except a~ hereinafter noted. Hence, only
one of each of them will be described in detail, and
their common component parts will be indicated by
same reference numerals.
The internal panel 14 includes a generally flat
1.5 body 38 that has a generally oval shaped peripheral
edge. An integral edge flange 42 projects
perpendicularly from the plane of. the 'body 38. The
panel 14 also includes upper, middle and. lower
circular apertures 44, 46 and 48, respectively, The
20 diameters of paired apertures are the same. These
apertures are, in turn, surrounded or circumscribed
by integral flanges 52, 54 and 56, respectively.
The inner diameter of the flanges 52, 54 and 56 are
the same as the diameters of the apertures 44, 46
25 and 48, respectively. These flanges project
generally perpendicularly from the plane of the
panel body 38. As noted, the structure of the
internal panel 16 is identical to that of panel 14.
The flow tube 18 is shorter in length that the
3d overall length of the muffler 12. The tube 18 has a
circular cross-sectional and its side wall, between
its ends 58 and 62, is perforated, as generally
indicated at 63, so as to permit the expansion of
exhaust gases within the muffler. An end 58 of the
35 tube 18 has an inner diameter that is preselected so
that it may receive an end of one of the end tubes
24 and 26 as hereinafter described. The other end
2054 fit
62 of the flow tube 18 is adapted to remain open and
free of contact with other tubes. The outer
diameters of the ends 58 and 62 are selected so that
they fit within the apertures 4~i, 4o and 48 and the
flanges 52, 54 and ~i6. Again, flow tube 22 is
structurally identical to the tube ,_8.
The internal panels 14 and 16 and the flow
tubes 18 and 22 are the components of. a reversing
unit sub-assembly, shown generally at 64. This sub-
LO assembly is fabricated by placing the internal
panels 14 and 16 in a spaced apart, parallel f.ash.ion
so that the apertures 44 and the apertures 46 in the
panels 14 and 16 are axial aligned and so that the
flanges 52, 54 and 56 of the panel face outwardly or
away from each other. The flow tube 18 is disposed
in the pair of aligned, upper apertures 44, and the
flow tube 22 is disposed in the pair of aligned
middle apertures 46. Specifically, the preselected
sized end 58 of the flow tube 18 is disposed within
the aperture 44 of the panel 14 while its other end
62 is disposed within the aperture 44 of the panel
16. Both of the ends 58 and 62 of the tube 18 are
surrounded by and fit closely within the aperture
flanges 52 of the panels 14 and 16. Similarly the
ends 58 and 62 of the flow tube 22 are disposed
within the apertures 46 of the internal panels 16
and 14, respectively, and fit closely within the
flanges 54 which surround the middle apertures 46 in
the internal panels.
As best illustrated in FIGURES 1 and 4, a
mechanical lock joint, generally indicated at s6, is
employed to lock the ends 58 and 62 of the flow
tubes 18 and 22 to the panels. This lock joint 66
is preferably that shown in U.S. Patent No.
4,570,747. As described in that patent, the lock
joint 66 includes a relatively small number of
circumferentially evenly spaced protrusions 67 that
2054962
~z
are generally hemispherical in confxgur;~tion" TheSP
protrusions h?, tcqether with the flaring of the
distal ends of the aperture flanges 5~ and 5a and of
the ends 58 and 62, serv,a to lock the flow tuhes 18
and 22. tn the panels 14 and ;6 so as to fs~rm the
relatively rigid sub-assembly 64.
The inner wrapper 3,.x is made from a generally
rectangular sheet metal panel. or sties=t tr.~ which
conventional tooling has been applied. The wrapper
1O is shaped or conffigured so that its inner surface
defines a generally oval shaped cross-ser_tional
volume that is congruent, in cross-section, to the
outer shape of the edge flanges 42 on the internal
panels 14 and 16. when thus folded or configured,
the adjacent, end edges of. the wrapper are joined
together although preferably they are seam locked in
a conventional manner.
After the inner wrapper 34 has thus been
farmed, the reversing unit sub-assembly 64 is
inserted inside it through one of the side openings
defined by one of the side edges of the wrapper.
The sub-assembly 64 is positioned or disposed within
the interior of the wrapper 34 such that the
internal panels 14 and 16 roughly divide the
interior into three equal chambers; a left hand
chamber 68, a central chamber ?2, and a right hand
chamber 74 as illustrated in FIGiTRE 1.
The edge flanges 42 of the internal panels 14
and 16 are in close contact with the inner wall of
3o the inner wrapper 34. >:lnlike prior mufflers, no
welding or other metallurgical bonding is needed to
hold the reversing unit sub-assembly 64 in place
within the inner wrap 34_ The close contact between
the end flanges 42 and the inside surface of the
inner wrapper 34 serves to retain the sub-assembly
64 in place during subsequent assembly of the
muffler 12. It is, however, contemplated that in
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13
certain inward defor-nations of the wrapper 34, on
both sides of each edge flange 4.~~, may be 'used to
"trap" the panels 14 that is, assist in holding the
panels) vis-a-vis the wr<~pper. As noted, the fact
that the panels 14 do not need to be secured to the
wrapper 34 by welding or some other metallurgical
bonding is an important advantage since, among other
things, welding or other metallurgical bonding
usually de:>troys the integrity of the metal.
protective coating that is applied to the wrapper 34
and other components of the muffler 12.
After the reversing unit subassembly 64 is
disposed within the inner wrapper 34, the outer
wrapper 36 i.s shaped or configured about the inner
wrapper 34. Like the inner wrapper 34, the outer
wrapper 36 is made from a generally rectangular
sheet metal panel sheet that is shaped or configured
about the outer surface of the inner wrapper 34 so
that it closely conforms with the outer shape or
configuration of the inner wrapper. The adjacent,
end edges of the outer wrapper 36 are then joined
together, again preferably by seam locking them in a
conventional manner. The side edges of the outer
wrapper 36 are generally aligned with and closely
adjacent to the side edges of the inner wrapper 3.4.
The Left and right pairs of side edges of the
wrappers 34 and 36 are respectively indi.~::ated at 76
and 78 in FIGURE 1.
Two end cap sub-assemblies 82 and 84 a_re next
assembled onto the muffler 12 during its
fabrication. Each of these sub-assemblies is
structurally and functionally identical except as
hereinafter noted. Because of this, only one of
these sub-assemblies 82 and 84 will be described in
detail but the same reference numerals will bs~ used
to indicate identical parts in both.
Referring now to FIGURES 2 and 3, the end cap
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sub-assembly 82 comprises the end tube 24 r!nd the
end panel ?.8. As hereinafter diso_us sf.d, the end
tube 24 is mounted on the end panel 28 si.zch that the
longitudinal axes of the tubes 18 and <>.4 are
substantially aligned when the sub-ass<~mbly 82 is
assembled or mounted on the left hand end of the
muffler 12, as shown in FTGURE 7.
End tuhe 24 includes an inner end B6 and an
outer end 88. The tube :?4 i.s of uniform diameter
1~ except adjacent to i.ts inner end 86. At that end,
it is swaged down or otherwise reduced in s:i 2e so
that its outer diameter has a preselected size,
relative to the inner diameter of the end 58 of the
flow tube 18. More specifically, the outer diameter
15 of the inner end 86 of the tube 24 is preselected
whereby it can be telescopically, overlapping:ly and
importantly, loosely and easily interfi.tted within
the end 58 of the flow tube 18. The 'Length of the
inner end 86 is also preselected, its preselected
20 length permits it to be telescopically received
within the end 58 so that its distal end may be
disposed or located beyond the plane of the body 38
of the internal panel 14. Because of the
differences in the sizes of the outer diameter of
25 the end 86 and the inner diameter of the end 58 ---
which results in a :loose fit therebetween -~- the
insertion of the end 86 of the tube 24 within the
end 58 of the tube 18 does not apply any significant
forces to the flow tube 18 or the sub-assembly 54,
30 and accordingly, cannot and does not cause any axial
displacement of the subassembly 64, including the
panels 14 and 16 , with respect to the wrapper_ s 3 4
and 36.
A clearance of .030 inches between these tube
35 ends 58 and 86 has generally been found to be
satisfactory. For example, where the nominal :inner
diameter of the end 58 of the flow tube 18 is 1.94
24x4962
,S
inches, the nominal outer diameter of the reduced
inner end 86 of the end tube ~:: wo~alc9 be 1..91
inches, with a tolerance of plus or minus .010
inches.
As il7.ustrated in FIGZIRF 1 , the tube 22 is
positioned in the middle apertures 54 of the
internal panels 14 and 16. The tube 7.6 is mounted
on and positioned, with respect to the end cap sub-
assembly 84, so that the longi.tudi.nal axes of the
tubes 22 and 26 are aligned when the sub-assembly 84
is mounted or assembled on the right end of the
muffler 12. The reduced inner end 86 of the tube 26
is disposed within the receiving end 58 of the flow
tube 22 in a similar fashion.
The outer end 88 of the tube 24 includes a
relatively large diameter flange 92. This flange
may be attached to the tube 24, for example, by
conventiona:L welding techniques, and is adapted to
connect the tube 2.4 , and thus the sub--assembly 82
and the entire muffler 12, to other parts of the
vehicular exhaust system, not shown. For this
purpose, the flange 92 includes a plurality of bolt
receiving holes 94, as shown in FIGi7RE 1.
The peripheral. shape of the end panel 28 is
congruent with the opening defined by the side edges
76 of the inner and outer wrappers 34 and 36. It is
sized so that the panel 28 covers or ''fill;s" that
opening and sa that its peripheral edge is adjacent
to the side edges 76 of the inner and outer wrappers
34 and 36. The panel's peripheral edge 96 and the
side edges 76 are joined together_Y preferably by
spinning and crimping in a conventional. matter, to
close the opening defined by the side edges 76.
Alternatively on some mufflers, only the inner
wrapper i.s mechanically locked with the peripheral
edge 96 while the side edge of the outer wrapper is
"trapped" between the spun edges of the end panels
205492
an<-3 the inner wrapper.
With reference tc~ FIGiIRFS 1 and 'l, a circular
aperture 9A is in the panel 28 and is surrounded by
an integra'A. generally perpenc3icul<-~rly projecting
f l ange 1 n:' . The S 1 2e (7f tile apP.Yture 9 R i S SE?1 eCted
so that it tightly receives the end tube 24, between
its ends. When the end cap sub-assembly 8?. is
assembled or mounted an the muffler 1?., the flange
102 is direcaed toward the sub-assembly 64, that is,
toward the end 86 of the tube 24.
An improved mechanical, gas tight, torque lock
joint 104 attaches the end tube 24 within the end
panel aperture 98 and to the end pane2 28.. This
lock joint 1.04 includes a substantially continuous
circumferential bead ?.06 formed in the part of the
tube 24 adjacent to the left or outwardly facing
side ( as shown in FIt~rJRE 1 ) of the end panel 28 .
The plane of this bead 1.06 i.s substantially
perpendicular to (or at an angle of 90°') with
2U respect to the longitudinal central. axis of t:he tube
24. The protruding portion of the bead 106 has a
diameter which is greater than the diainster of the
aperture 98 and is positioned so that the inner
facing side of the bead abuts or contacas the
adjacent part of the panel 28. The bead 106 has a
generally semicircular cross-section, taken
perpendicular to the plane of the bead, but has
somewhat of a segmented, or interrupted appearance
as a result of it being formed by the a=_;e of a
segmented, expanding mandrei.
The lock joint 104 also includes a series of
spaced apart, circumferential aligned and equi-
spaced, elongated deformations or protrusions 108
that are formed in the portion of the end tube 24
underlying the flange 102 and alsca ir7 the flange
102.' These deformations are formed sa that their
outer side abut or contact the adjacent part of the
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panel 28 . The outer '-ad i a7 d amete:r or di mensi inns
of thesA riaformation~; 10R is larger than the
diameter of the aperture 9R. The plane of these
deformations 10t3 is perpendicular to for at an angle
of essentially 90°) with respect to the longitudinal
central axis of the end tube 24. The. major axes of
these deformations 108 are preferably aligned with
this plane of the deformations. However, the
deformations 108 w 1l also serve to increaese the
torsional strength of the joint 104 if them- major
axes are aligned at other angles with respect to the
plane of the deformations. The circumferent:ial
distance between adjacent deformations 108 is about
one half of the circumferential length of the
deformation.
As an example of the relativa_ dimensions
involved, where the nominal outside diameter of the
end tube 24 is 2.00 inches and where the diameter of
the aperture 98 is 2.00 inches, the outer diameter
of bead 106 .is 2.25 inches, and the outer diameters
of the deformations 108 are 2.25 inches. In such a
lock joint 104, there will be as many as 12
deformations 108, each having a length in the plane
of the deformations, of approximately 0.31 inches
and a width, in a direction parallel to the
lorigitudinal. central axis of the tube 24, of
approximately 0.21 inches.
The bead 106 and deformations 108 of t'he lock
joint 102 may, as noted above, be formed by
inserting conventional tooling, such as a segmented
expanding mandrel within the end tube 24. Once
inserted anc9 appropriately located with respect to
the panel 28, the tooling is expanded in a
conventional manner. Back-up dies are, however, not
required to form a bead and the deformations that
will satisfactorily attach the end panel 28 and the
end tube 26 together and will support the torsional
,g 2Q54962
loads appl;ed to the tutee ?4. This maiCes the
overall. too:ina sianifi.cantly less expensive and the
fabrication of tie joint 104 much less tpme
consuming.
As noted above, when the end c:ap sub-assembly
82 is assembled or mounted on the left hand end (as
shown in FICzURE 1) of the muffler 1;~, the inner end
86 of the end tube 24 is loosely interfitted within
the end 58 of the f?ow tube 18. As also noted
1.0 above, the length of the inner end 86 .is selected
such that its distal end extends into the end 58 to
a point beyond the plane of the body 38 of internal
panel 14. Although the tolerances an the exact
location of the distal end of the end 86, vis-a-vis
the body 38, are not particularly close or critical,
it should extend beyond the plane of the body 38 by
at least approximately 0_51 inches.
The inner end 86 of the tube 24 is locked
within the end 58 by a novel mechanical, gas tight
lock joint 112. It is because of the use of this
lock joint 112 that the exact position of. the distal
end of the end 86 vi.s-a-~vis the plane of body 38,
the tolerances between the outer diameter of the
inner end 86 and the inner diameter of the end 52
are not critical and are much more relaxed than were
required when the inner end of the end tube had to
be press fit within a flow tube. This easing or
relaxation of the manufacturing tolerances, of
course, reduces the costs of and time required for
assembling the muffler 12.
More specifically, the lock joint 112 comprises
a continuous, circumferential, skewed bead 114 that
is formed in and between portions of the inner end
86, the end 58 and the flange 52.. The bead
generally describes an ellipse or oval in the flat
plane of this bead, which plane is skewed or
disposed at an oblique angle, that is, an angle less
2o54~s2
than 90°, with resner_t to the central longitudinal
axes of the end and flow tubes. Preferably, this
angle is approximatel~~ 75 degrees.
Because of this skewing of tha b~sad 114, the
bead intersects and crosses the plane of the body 38
of the internal panel. 14. Specifically, and as best
shown in FIGURES l and 5, portions of the bead 114
are formed in and between the flange 5?., the
underlying distal end of the end 58, and the
underlying part of the inner end 86 that are to the
left of the plane of the body 38. Other portions of
the bead 114 are formed in and between the inner end
86 and the overlying part of the flange 52 that are
to the right of the plane of the body 38. More
specifically, the bead 1.14 maintains the relative
axial pasiti.ons of the overlapped ends of the tubes
18 and 24 and resists relative movement between the
overlapped ends due to the applicatian ~rf torsional
and axial farces that these tubes experience during
the assembly of the muffler 1.?.. The bead 114 is
substantially continuous and extends beyond the
plar!e or side surface of the panel 14 on the panel's
right hand side, as seen in FIGURE 1, and beyond the
distal end of the flange 52 on the left hand side.
Because it is preferably made by a conventional
segmented, expanding mandrel, it has somewhat of an
interrupted or segmented looking appearance.
Generally speaking, however, it has a semi-circular
cross-section.
ns an example of the perti.~.ent relative
dimensions, the bead 114 has a ma~ar diameter of
approximately 2.12 inches and a minor diameter of
approximately 2.00 inches when used with tube 18 and
24 where the outer diameters of the inner end 86 and
the end 52 are approximately 1.94 and 2.06 inches,
respectively. Generally it has a cross-sectional
shape with a radius of about 0.09.
2054962
As noted, the bead 114 rnay tae formed by
conventi.onaL tooling nct shown. Sa:ch tooling may be
inserted into the enr3 tube 2~ through its other or
outer end 88 when the sub-assembly 82 i.s assembled
5 or mounted on the muffler 12. Dike the bead 106 and
deformations 108 formed in the lock joint 1.04, the
bead 114 can be satisfacaorily formed without the
use of back up dies. This significantly reduces the
cost of the overall tooling and requires much less
10 time to form the bead while permitting the bead to
provide both axial and torsional support for loads
applied to the lock joint 13.?..
The end cap sub-assembly 84 i_s assembled or
mounted on the right hand side, as seen in FIGURE 1,
15 in the same manner as sub-assembly 82 is assembled
on the left hand side. The only structural
difference is that the aperture 98 in the panel 32
is aligned with the middle aperture 46 of the
internal panel 16. This permits the inner end 86 of
20 the end tube 26 to loosely interfit and overlap
within the end 58 of the flow tube 22.
When the muffler is assembled as described
above, exhaust gases from the exhaust system may,
for example, enter the muffler through the end tube
24. These gases then flow into the interior of the
flow tube a8 where they can escape or expand,
through the perforations in that tube, into the
center chamber 72. the gases may additionally flow
into the right hand chamber 74 through the open end
62. The exhaust gases may also flow between the
chambers 68, 72, and 74 through the apertures 56 in
the internal panels 14 and 1.6. The gases pass into
the interior of the flow tube 22, through the
perforations therein, as well. as through its end 62.
The gases then pass into the end tube 26 and out of
the muffler through the other end 88 of the tube 26.
The preferred embodiment of the present
2054962
invention has now been des.~.rihed. This preferrer3
Pmbodi.ment c:onstitutPS the best mode contemplated by
the inventars for carrying out their present
invention. The inventi.an, and the manner and
process of making and using it, have been described,
it is believed; in such fuil., clcaat-, concise and
exact terms as to enable any person skil2ed i.n this
art to make and use the same. Because the present
invention may be copied, without copying the precise
details of the preferred embodiment, the following
claims particularly point out and distinctly claim
the subject matter which the inventor; regard as
their invention and wish to protect.
