Note: Descriptions are shown in the official language in which they were submitted.
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CBB992
TUBE END-FORMING METHOD AND APPARATUS
S
FIELD OF THE INVENTION
This invention relates to a method and apparatus for performing operations on
the
end of a part such as a tube, pipe and the like; and, particularly, changing
an elliptical,
oval or similar non-circular mouth of said part to an essentially circular
mouth.
BACKGROUND OF THE INVENTION
Many systems, such as exhaust treatment devices, require formed tube of
considerable complexity in shape and size and may, in some circumstances,
involve the
production of metal tube with varying diameters and cross-sectional shapes.
Over the
length of such an exhaust system, the cross-sectional area and shape may
change
numerous times to satisfy requirements of the system. Exhaust treatment
catalytic
converters having an oval or elliptical shaped tube are just one type of tube
that carries
hot exhaust gases to and from the system.
There are many reasons why the cross-sectional diameter and/or shape of a tube
is
varied. One reason is to utilize space that is not already accounted for but
already
necessary in the shell of a machine "reduced packing factor". Another reason
is a result
of a tube path restriction where it is more economical to change the shape of
the tube than
to re-rout the path of the tube. In a situation where a circular cross-
sectional part would
be normally preferred but the space available confines its installation in
only one
direction, say, for example, the vertical axis but not in the horizontal
direction
perpendicular to the vertical axis, the designer may choose to use an
elliptical or oval
cross-section tube of similar cross-sectional area.
In the automotive industry, for example, there is an increasing need to
manufacture more complex tubular shapes that are more economically viable.
Further,
since emission controls on exhaust systems have become more and more limiting,
there is
a need to produce these systems of a leak-proof construction. However,
problems
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associated with the manufacture of prior art exhaust treatment devices
generally result in
unwanted leakage of gases from the container of the device itself and
premature failure.
Prior art so called "clamshell" converters are made from two stamped halves
which form
the body of the exhaust treatment device. The substrate and sealing components
are fitted
between the two halves and the resultant shell then seam welded. Variations in
the
substrate dimensions resulting from such manufacture often results in the
converters
"rattling" and leaking. Further, because the treatment device housing is made
from
stamped pieces, it is difficult to obtain a consistently tight fit between the
housing and the
substrate. Further, desirable manufacturing processes must eliminate or reduce
the
creation of defects, such as wrinkles, kinks and the like, on the shells of
these tubes.
Current methods that are practiced to fabricate a section which contains an
oval
cross-section and cylindrical inlet andlor outlet leads usually incorporate
the aforesaid
joining process, whereby multiple parts are combined by welding, swaging or
equivalent
treatments to combine multiple parts.
Methods and apparatus are known for reducing an end portion of a tube having a
first circular cross-section to a second circular cross-section of smaller
diameter by means
of feeding the end portion in a forming tool comprising a plurality of
adjustable jaws
having a cumulative inner surface defining a fructo-conical shape to
symmetrically
contact the outer surface of the end portion with the inner surface of the
forming tool and
subjecting the end portion to a symmetrical force to effect circular cross-
section diameter
reduction.
Method and apparatus are also known whereby an end portion of a tube having a
circular cross-section is non-symmetrically expanded to an oval or elliptical
cross-section
by means of a ram tool comprising one tapered die operably rammed within the
end
portion of the tube and effecting even expansion of the circular end along one
axis only
to form the oval part.
However, the use of a mufti jawed tool to change the cross-sectional shape of
an
end portion of a tube to essentially circular from oval or elliptical, to-
date, is novel and
provides an advantageous solution to the aforesaid disadvantages of apparatus
and
methods for making exhaust gas treatment devices.
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SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method of changing the
shape
of an end portion of a tube having an elliptical or like oval cross-section to
an essentially
circular cross section.
It is a further object to provide apparatus for effecting said change in said
end
portion.
Accordingly, in one aspect the invention provides a method of reducing an end
portion of a tube having an oval or elliptical cross-section with a radial x-
axis longer than
its radial y-axis perpendicular thereto, to an essentially circular cross-
section, said method
comprising feeding said end portion to a forming tool comprising a plurality
of
adjustable, segmented jaws having a cumulative inner surface defining a cavity
having
(a) an entry aperture defining an oval or elliptical cross-section with a
radial
x-axis longer than its radial y-axis perpendicular thereto, said aperture
adapted to operably receive said end portion of said tube in surface
abutment therewith;
(b) an essentially circular cross-section operably of the same radial length
as
said radial y-axis of said tube inner portion of said cavity; and
(c) an intermediate portion between said aperture and said inner portion
defining a surface of reducing cross-section along said radial x-axis;
and subjecting said end portion within said cavity to a sufficient force to
effect reduction of said radial x-axis relative to said radial y-axis to
produce said end portion having said essentially circular cross-section
The invention is of particular value in producing an oval tube having a round
end
or two round ends, which is formed from a single oval piece. The resultant
oval tube
portion provides for reduced space requirements, for example, beneath an
automobile,
truck and the like, while having inner components, such as a catalytic
converter system,
between its two round ends. The round ends enable suitable connections to be
made to
other round conduits and the like.
The present invention relates in one embodiment to a metal tube end forming
machine and process, and , particularly, for deforming at least one end of a
hollow metal
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tube or pipe with a generally oval cross-section in such a way that the end is
converted to
an essentially circular cross-section. The resulting circular cross-section,
may, but not
necessarily, have a smaller diameter than the originating minor diameter of
the y-axis of
the oval or elliptical cross-section.
In a further aspect the invention provides apparatus for reducing an end
portion of
a tube having an oval or elliptical cross-section, said apparatus comprising
(i) a forming tool comprising a plurality of adjustable, segmented jaws having
a
cumulative inner surface defining a cavity having
(a) an entry aperture defining an oval or elliptical cross-section with a
radial x-axis
longer than its radial y-axis perpendicular thereto, said aperture adapted to
operably
receive said end portion of said tube in surface abutment therewith;
(b) an essentially circular cross-section operably of the same radial length
as said
radial y-axis of said tube inner portion of said cavity; and
(c) an intermediate portion between said aperture and said inner portion
defining a
surface of reducing cross-section along said radial x-axis;
and subjecting said end portion within said cavity to a sufficient force to
effect
reduction of said radial x-axis relative to said radial y-axis to produce said
end
portion having said essentially circular cross-section.
(ii) means for feeding an end portion of a tube having an oval or elliptical
cross-
section to said entry aperture of said cavity;
(iii) means for reducing said end portion through said cavity to effect
reduction of said
end portion to a circular cross-section; and
(iv) means for releasing said end portion from said forming tool.
The present invention provides a new and improved method for fabricating an
end
of a tube, pipe and the like to a suitable circular shape as a one-piece tube,
while retaining
the oval cross-sectional shape of the non-end portions of the tube, so as to
advantageously
reduce the packing factor of the manufactured part and eliminate the need to
use welding
and like tools to join two semi-shell parts and reduce the cross sectional
area and volume
of the installed tube. Additionally, the resultant suitably shaped tube made
according to
the fabricating method of the invention limits the likelihood of the tube
leaking fluid,
particularly, hot exhaust gas. Further, the costs of manufacturing an
equivalent tube by
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eliminating the need to weld or join multiple parts to form an equivalent
internal profile,
are reduced.
Surprisingly, we have found that the process of the invention does not cause
the
tube material to become unsatisfactorily work hardened in consequence of the
deforming
5 the oval tube material to the desired extent. Work hardening is a material
effect that
occurs in metals during forming to cause it to become brittle and result in
tearing or
breaking during a reshaping operation.
BRIEF DESCRIPTION OF THE DRAWINGS
In order that the invention may be better understood, a preferred embodiment
will
now be described by way of example only, with reference to the accompanying
drawings
wherein
Fig. 1 is a diagrammatic perspective view of forming apparatus according to
the
invention;
Fig. 2 is a perspective view of a forming tool of use within the apparatus of
Fig. 1;
Fig. 3 is a perspective view of the forming tool of Figs. 1 and 2, partially
broken away by
removal of two jaws;
Fig. 4 is a perspective view of an oval automotive exhaust tube prior to
forming
according to the invention;
Fig. S is end, side and perspective view of the completed interface indicating
the oval
cross section being reduced to a circular cross section of diameter smaller
than both the
maj or and minor diameters of the oval tube;
Fig. SA represents a perspective view of a reduced exhaust tube manufactured
according
to the process of the invention;
Fig. SB is a diagrammatic side view of the tube of Fig. SA;
Fig. SC is a front view of the tube of Fig. SA;
Fig. 6 is a sectional view of one opposing pair of jaws showing internal
elements of the
tool including the same features which allow the plurality of jaws to retract
radially; and
wherein the same numerals denote like parts.
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DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
With reference to Fig. 1, this shows, generally as 10, a Model HP90 machine
head
12, commercially available from Eagle-Eaton Leonard, Brantford, Ontario,
Canada,
S having a front plate 14 in a forward position to enable a forming tool shown
generally as
16 to be seen on head 12. Front plate 14 has an axial aperture 18 defined by a
fructo-
conical inner surface 19 of plate 14.
Tool 16 has a barrel assembly 20 and a plurality of adjustable, segmented jaws
21
which cumulatively defines a fructo-conical outer surface 22 complimentary to
and
operably received by inner surface 14, when plate 14 is operably moved axially
forward
of too116 on a pair of shafts 24, by mechanical means (not shown). Jaws 21
cumulatively
have an inner surface 26 which defines an inner cavity 28 which operatively
receives an
automative exhaust gas tube 30 shown in ghost lines and in Fig. 4.
With reference to Fig. 2, cumulative inner surface 26 defines cavity 28 having
(i) an entry aperture portion 32 having an oval or elliptical cross-section
with a radial
major or x-axis xl longer than its radial minor or y-axis, y', perpendicular
thereto;
(ii) an essentially circular cross-section inner portion 34 operably of the
same radial
length as the narrow or y-axis of tube 30; and
(iii) an intermediate portion 36 between aperture 32 and inner portion 34
defining an
inner surface 38 of reducing cross-section along radial x-axis such that the
length of xl
tends to that of y'.
With reference to Fig. 6, barrel assembly 20 has a plurality of compression
springs 40, equivalent in number to jaws 21, being 8 in the embodiment shown.
Jaws 21
are suitably arranged to expand and contract subject to the radial limits
imposed by barrel
assembly 20 and a retention band 42. Springs 40 are sandwiched between
adjacent jaws
21 and provide the means to encourage jaws 21 to expand and maintain a gap 44
between
adjacent jaws 21. Band 42 is wrapped around an outer surface portion of jaws
21 and
provides alignment to jaws 21 when the jaws expand. In alternative
embodiments, other
numbers of jaws and jaw arrangements may be used. Preferably, a minimum of
four,
most practically 4 - 16, and most preferably, 8 - 16 jaws.
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Segmented jaws 21 collectively provide the vehicle to radially deform segments
axial of the length of the portion of the oval tube to provide a gradually
reduced,
deformed end tube portion. Major x-axis jaws 46 deforms oval tube 30 major or
x-axis
diameter to a greater extent than minor diameter jaws 48 deforms tube 30 minor
diameter
segment the least.
Fig. SA is end, side and perspective view of the completed interface
indicating the
oval cross section being reduced to a circular cross section of diameter
smaller than both
the major and minor diameters of the oval tube.
Thus, the plurality of jaws 21 can be divided into two main working elements,
i.e.
an internal geometry and an external geometry, which provides the means to
radially
contract the plurality of jaws 21.
External cone surface 22 of the plurality of jaws 21 is axially symmetrical of
the
jaws and is designed to mate within aperture 19 and provides the means to
radially
contract the plurality of jaws 21 and, thus, the oval tube in the inner cavity
28.
Segmented-reshaping-tool 16 may be considered to comprise a hollow geometry
that matches the transition area 50 of completed oval tube product 52 - Figs.
SA - SC.
The shape and diameters of the leading cross-sectional surface 54, at the open
end i.e.
aperture 32 of segmented-reshaping-tool 16 in its closed position is designed
to match the
shape and diameters oval tube 30 prior to end forming. The shape and diameter
of the
finishing cross-section surface 56, at the internal end tool 16, in its closed
position is
designed to match the transition area 50 of tube 30 and have a final opening
of circular
cross-section 58. The transition cross-sectional-surface 36 is the surface on
tool 16
between leading cross-sectional-surface 32 and finishing cross-sectional-
surface 34, in
the closed position, and is designed to "blend" the leading and finishing
cross-sectional-
surfaces 32, 34 of tool 16 and match the profile and contours of the completed
oval tube
52.
In operation, oval tube 30 is aligned with tool 16 and secured by means of an
oval
tube clamp 60 in a position such that the centers of both oval tube 30 and 16
are
concentric. Clamp 60 eliminates the movement of tube 30in all directions.
Clamp 60 has
means (not shown) to move a clamped tube 30 in a series of steps towards tool
16. The
clamp's means is independent of front plate 14.
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Segmented forming tool 16 is contracted by means of moving front plate 14
towards and over external cone surface 22. Whereby inner surface 19 of plate
14 applies
an outward radial force against external cone surface 22 to effect a
contraction of
segmented jaws 21 which in turn apply inward radial forces against opposing
surfaces of
tube 30. In their closed position, the plurality of jaws 21 has no gaps 44 in
its diameter.
As front plate 14 and inner surface 19 retract from the plurality of jaws 21,
tool 14
becomes free to expand under influence of compression springs 20.
In more detail, the operation of reducing an oval-sectional tube 30 a circular
cross-section is as follows.
Oval tube clamp 60 is fed into tool 16 so as to align the leading cross-
sectional-
surface 32 and leading surface of oval tube 30. The opened tool 16 is then
closed by
moving front plate 14 towards tool 16 wherein surface 19 exerts a radial force
over
surface 22 to cause radial contraction of segmented-reshaping-tool 16 and
pressing
leading cross-sectional-surface 32 onto aligned surface of oval tube 30 to
effect
deformation of it in such a manner as to match the complimentary profile of
cross-
sectional surface deformation of 32. Closed tool 16 is then opened by means
moving
front plate 14 axially from tool 16, which, in turn, effects expansion of
segmented-
reshaping-tool jaws 21 and release of partially formed oval tube.
Tube clamp 60 is then advanced further into segmented-reshaping-tool 16 so as
to
expose the next portion of tube 30 to tool 16. This cycling process is
repeated
continuously by means of a cooperative movement among oval tube clamp 60
feeding
mechanism and the opening and closing of jaws 21 until the desired oval
interface
reaction has been completed. The number of cycles necessary to complete a
finished
interface is dependent on oval tube's 30 geometry, composition and processing
history,
and the shape of the transition cross-sectional surface. In one embodiment,
one end of an
oval tube manufactured by the welding of a 3.5 mm thick 409 stainless steel
sheet and
having a major diameter i.e. xl of approximately 100 mm and a minor diameter
i.e. yl of
60 mm can be reduced to a circular diameter of 50 mm according to the present
invention
by use of a segmented-reshaping-tool 16 having an axial length of
approximately 75 mm,
a straight taper between the leading and finishing transition cross-sectional
surface 32, 34
in a series of steps, wherein plate 14 and tool 16 are cycled and tube clamp
60 is
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advanced, relatively one to the other approximating 5 - 15 mm at a machine
cycle rate of
approximately 6 cycles per second.
After the full forming process is completed, oval tube clamp 60 is retracted
to its
unload position in one continuous motion and end-formed tube 30 removed from
clamp
60.
Clearly, there are practical geometrical limitations to the shape of the
cumulative
inner surface of jaws 21 The inner surface angle between an axial segment
within jaws
21 and its axial axis cannot exceed some maximum angle. Beyond this maximum
angle,
the force necessary to feed the tube end portion into jaws 21 becomes too
large and
causes the tube wall to collapse in the tube axial direction. Additionally,
the ratio of oval
tube's 30 major diameter to minor diameter must be considered in that if this
ratio
exceeds a certain value oval tube 30 wall at its minor diameter will collapse.
These
geometrical limitations can be readily determined by the person skilled in the
art from a
consideration of tube material, thickness and the unlisted and final end
formed shapes.
Although this disclosure has described and illustrated certain preferred
embodiments of the invention, it is to be understood that the invention is not
restricted to
those particular embodiments. Rather, the invention includes all embodiments
which are
functional or mechanical equivalents of the specific embodiments and features
that have
been described and illustrated.
