U.S. patent application number 09/321579 was filed with the patent office on 2001-11-15 for flexible line element.
Invention is credited to ASCHOFF, WOLFGANG, SALZER, GEORG.
Application Number | 20010040375 09/321579 |
Document ID | / |
Family ID | 7869330 |
Filed Date | 2001-11-15 |
United States Patent
Application |
20010040375 |
Kind Code |
A1 |
ASCHOFF, WOLFGANG ; et
al. |
November 15, 2001 |
FLEXIBLE LINE ELEMENT
Abstract
A flexible line element, particularly for exhaust pipes of
internal combustion engines of motor vehicles, is characterized in
that it has at least two interconnected, metal bellows provided
with cylindrical joining ends and at least one of the bellows is
helically corrugated. This and/or the bellows are telescoped and
two bellows are connected at only one of their joining ends. A line
element constructed in this way is on the one hand torsion-soft, so
that it does not transfer any torsional stresses to adjacent
components, and on the other is also stable in the case of high
torsional stresses.
Inventors: |
ASCHOFF, WOLFGANG;
(AKAZIENSTR, DE) ; SALZER, GEORG; (JURASTR,
DE) |
Correspondence
Address: |
ANTONELLI TERRY STOUT AND KRAUS
SUITE 1800
1300 NORTH SEVENTEENTH STREET
ARLINGTON
VA
22209
|
Family ID: |
7869330 |
Appl. No.: |
09/321579 |
Filed: |
May 28, 1999 |
Current U.S.
Class: |
285/227 |
Current CPC
Class: |
F16L 27/11 20130101;
F01N 13/1816 20130101 |
Class at
Publication: |
285/227 |
International
Class: |
F16L 021/00 |
Claims
1. Flexible line element, particularly for exhaust pipes of
internal combustion engines for motor vehicles, wherein at least
two interconnected metal bellows provided with cylindrical joining
ends are present and at least one of the bellows is a helically
corrugated bellows:
2. Flexible line element, particularly for exhaust pipes of
internal combustion engines for motor vehicles, wherein at least
two interconnected metal bellows provided with cylindrical joining
ends are present and wherein the bellows are telescoped and wherein
two bellows are connected at only one of their joining ends.
3. Line element according to claim 1 or 2 comprising exactly two
bellows.
4. Line element according to claim 1, wherein the bellows (1, 1a or
1, 2) are successively arranged.
5. Line element accorrding to claim 1 or 2, wherein at least one
bellows (1) is helically corrugated and at least one other bellows
is annularly corrugated.
6. Line element according to claim 1 or 2, wherein at least two
bellows (1, 1a) are helically corrugated and have a thread with an
opposing pitch.
7. Line element according to claim 1, wherein the bellows are
telescoped and two bellows are connected at only one of their
joining ends.
8. Flexible line element according to claim 1 or 2, wherein one
joining end of a first bellows is firmly connected to one joining
end of the other bellows and the other joining end of the first
bellows is firmly connected to one end of a substantially rigid
pipe element, the other end of the pipe element serving as one
cylindrical joining end of the line element and the other joining
end of the outer bellows serving as the other cylindrical joining
end of the line element.
9. Line element according to claim 7, wherein a joining end (3a) of
the inner bellows arranged internally of the line element is firmly
connected to one end of the pipe element, whilst the other end of
the pipe element arranged internally of the inner bellows serves as
a cylindrical joining end of the line element.
10. Line element according to claim 2 or 7, characterized in that
at least two bellows are helically corrugated and have a thread
with a pitch in the same direction.
11. Line element according to claim 1, wherein that at least two
bellows have the same thread height h.
12. Line element according to claim 2 or 7, wherein that the
internal diameter of an outer bellows is larger than the external
diameter of an inner bellows.
13. Line element according to claim 11, wherein the internal
diameter of the outer bellows is smaller than the external diameter
of the inner bellows.
14. Line element according to claim 1 or 2, characterized in that
the one or more helically corrugated bellows have a multithread
construction.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a flexible line element,
particularly for exhaust pipes of internal combustion engines of
motor vehicles.
BACKGROUND OF THE INVENTION
[0002] Flexible line elements are e.g. incorporated as adaptors
into the exhaust pipe of a motor vehicle, which is installed on the
vehicle floor, in order to absorb movements and vibrations and
prevent the transfer thereof to adjacent components, such as arise
due to elastically mounted driving engines, vehicle faults,
temperature-caused length changes, etc. They generally comprise a
helically or annularly corrugated metal bellows, together with
further elements, such as line and/or support elements, together
with additional elements for supporting and/or increasing
stability, e.g. metal gauze, or damping elements, so that if
vibrations are excited in the resonant frequency range of the
bellows movement increases of the latter are prevented, because
they could lead to a reduction of the service life and to
interaction with other components for noise production
purposes.
[0003] In many cases flexible line elements of this type are
exposed to torsional stresses. If the bellows of such line elements
has a torsion-stiff construction, such as e.g. a parallel bellows,
although such torsional stresses do not lead to its failure, they
are transferred in undesired manner to adjacent components. If the
bellows is torsion-soft, it is suitable for the decoupling of
adjacent components, but in particular dynamic torsional stresses
can lead to Its failure. It is stressed in this connection that in
the case of dynamic stressing a metallic material is subject to
earlier fatigue than with static stressing, the stresses to which a
line element in the exhaust pipe of a vehicle is exposed being more
particularly of a dynamic nature.
[0004] Thus, on the basis of a line element of the aforementioned
type, one object of the invention is to design it in such a way
that it is compact and especially may have short axial extension. A
further object of the invention is to achieve that the line element
is on the one hand torsion-soft, so that it does not transfer
torsional stresses to adjacent components, but on the other that it
does not fail when high torsional stresses occur.
SUMMARY OF THE INVENTION
[0005] According to the invention, the problem is solved in the
case of a line element of the aforementioned type in that there are
at least two interconnected metal bellows provided with cylindrical
joining ends and at least one of the bellows is a helically
corrugated bellows and/or that the bellows are telescoped and that
two bellows are connected at only one of their joining ends. One
joining end of a first bellows is firmly connected to one joining
end of the other bellows and the other joining end of the first
bellows is firmly connected to one end of a substantially rigid
pipe element, the other end of the pipe element serving as one
cylindrical joining end of the line element and the other joining
end of the outer bellows serving as the other cylindrical joining
end of the line element.
[0006] The twistability of the inventively designed line element is
based on the physical similarity of a helically corrugated metal
bellows and a coil spring. If a coil spring is lengthened or
shortened, it is subject to a restoring force F, which is
proportional to the deflection s, the proportionality factor D
being the spring strength:
F=D.times.s
[0007] In the case of a deflection s the coil spring starts to
twist about its median longitudinal axis, the twisting about the
latter being proportional to the deflection. Conversely a coil
spring is able to transform a torsional stress into a length
change, the restoring force F proportional to the deflection
consequently being proportional to the twisting about its median
longitudinal axis. Thus if several coil springs are combined with
one another, the individual springs can transform torsional
movements into axially directed, translatory movements, the
combination of coil springs being able to compensate
torsion-Induced, translatory movements.
[0008] As has already been stated, a helically corrugated bellows
behaves in a similar way. In the case of torsional stressing, it
transforms the twisting about its median longitudinal axis into a
length change and it is subject to a restoring force proportional
to the length change. If further axially flexible bellows are
combined with a helically corrugated bellows, then there is a
decoupling of torsional movements and translatory movements and it
is in most cases sufficient to only combine two bellows. At least
one bellows must be helically corrugated for transforming the
torsion into a length change, whereas the second bellows can either
be helically or annularly corrugated for compensating said length
change.
[0009] The torsion-softness of the inventive line element can be
adjusted via the geometry of the threads of the helically
corrugated bellow or bellows. The torsion-softness increases with
an increasing number of threads, for a constant thread pitch. In
addition, the torsion softness increases with increasing thread
pitch for a constant number of threads. If a particularly
torsion-soft line element is to be provided, it should consequently
have at least one helically corrugated bellows with a large number
of threads with a high thread pitch.
[0010] In a preferred embodiment, the line element according to the
invention has successively arranged bellows, whose diameters are
roughly identical and which are interconnected, e.g. by welding at
in each case one of their cylindrical joining ends. As two bellows
are generally sufficient for decoupling torsional stresses
occurring in the exhaust pipe of a motor vehicle (namely a
helically corrugated bellows for transforming the torsion into a
length change and a further helically or annularly corrugated
bellows for compensating the length change), it is preferred for
cost reasons to use only two bellows as basic components of the
line element.
[0011] As has already been intimated, according to a variant a
helically corrugated bellows is combined with a further helically
corrugated bellows. In another variant a helically corrugated
bellows is combined with an annularly corrugated bellows. In both
cases a torsional deflection at one of the two ends of the
arrangement leads to a translatory displacement of the connection
point between the bellows due to the transformation of a rotary
movement into an axial movement of a helically corrugated bellows,
the end of the arrangement opposite to the introduction of the
torsional movement remaining idle. In order to e.g. compensate the
torsion-induced length increase of a helically corrugated bellows
by means of the length reduction of a further, series-arranged,
helically corrugated bellows, it is particularly appropriate to
combine helically corrugated bellows with opposing thread pitch,
but the same pitch height in succession so as to form a line
element. Thus, e.g. a torsion-induced shortening of one helically
corrugated bellows is compensated by the lengthening of the second
bellows and a torsional stress acting on a bellows is not
transferred in undesired manner in the form of a translatory
stress.
[0012] According to another preferred embodiment of the inventive
line element, there is a parallel arrangement of telescoped
bellows, whereof at least one is helically corrugated and are
interconnected, preferably in the vicinity of in each case one of
their joining ends, e.g. by welding. Thus, a joining end of the
inner bellows arranged internally of the line element is firmly
connected to one end of the pipe element, whereas the other end of
the pipe element arranged internally of the inner bellows serves as
a cylindrical joining end of the line element. In much the same way
as for the consecutive arrangement of the bellows, a torsional
deflection at one of the two ends of the parallel arrangement leads
to a translatory displacement of the connection point between the
bellows due to the transformation of the rotary movement into an
axial movement of a helically corrugated bellows, whilst the end of
the arrangement opposite to the introduction of the torsional
movement remains idle.
[0013] If the diameters of the telescoped bellows are chosen in
such a way that the internal diameter of the outer bellows is
larger than the external diameter of the inner bellows, it is only
appropriate to combine with one another in each case helically
corrugated bellows with the same number of threads and a pitch in
the same direction, so that the bellows engage on one another. As a
result of the friction of the contacting, helically corrugated
bellows, this arrangement leads to a higher torsional stiffness of
the line element.
[0014] Although fundamentally the helically corrugated bellows can
be constructed with one thread, according to a preferred
development, the helically corrugated bellows have a multithread
construction.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Embodiments of the arrangement of bellows of a line element
according to the invention are described in greater detail
hereinafter with reference to the attached drawings, wherein
show:
[0016] FIG. 1 A line element according to the invention with a
consecutive arrangement of two helically corrugated bellows with
opposing thread pitch.
[0017] FIG. 2 A line element with a consecutive arrangement of a
helically corrugated and an annularly corrugated bellows.
[0018] FIG. 3 A line element with a parallel arrangement of two
helically corrugated bellows with a large diameter difference.
[0019] FIG. 4 A line element with a parallel arrangement of two
helically corrugated bellows with a small diameter difference.
DETAILED DESCRIPTION RELATIVE TO THE DRAWINGS
[0020] FIG. 1 shows a line element according to the invention with
a consecutive arrangement of two helically corrugated bellows 1, 1a
with cylindrical joining ends 4a, 4b, 3a, 3b. They are here
interconnected in the vicinity of their joining ends 4b, 3a, such
as by means of a weld 5, but the line element could also be
constructed in one piece. The bellows 1, 1a have a roughly same
size thread pitch h in opposing directions.
[0021] A torsional movement acting on a helically corrugated
bellows is transformed into a length change, the restoring force
forcing the bellows into its inoperative position being
proportional to said length change and consequently to the torsion
thereof.
[0022] If now e.g. the joining end 4a of the bellows 1 is twisted,
the connection point 5 of the bellows is axially displaced in
translatory manner, because the helically corrugated bellows 1
transforms the torsional movement into a length change. For
compensating this length change, e.g. a shortening, the helically
corrugated bellows 1a with the opposing thread pitch expands, so
that there is no axial movement of the joining end 3b of the line
element and consequently no coupling of torsional movements with
translatory movements in the axial direction of the line element.
With such an arrangement of two helically corrugated bellows 1, 1a
the shortening of one bellows corresponds to the lengthening of the
other, the connection point 5 of the bellows being twisted, whilst
the joining end of the line element opposite to the introduction of
the torsional movement remaining idle.
[0023] FIG. 2 shows a line element with successive or consecutive
arrangements of two bellows of a flexible, twistable line element,
firmly interconnected by means of a weld 5 in the area of their
cylindrical joining ends 4b, 6a, a helically corrugated bellows 1
being combined with an annularly corrugated bellows 2. In this case
with twisting of one joining end of the line element the helically
corrugated bellows 1 e.g. shortens and there is a corresponding
lengthening of the annularly corrugated bellows 2, so that although
no coupling of torsional movements with translatory movements in
the axial direction of the line element takes place, at least part
of the torsional stress acting on one joining end of the line
element is transferred.
[0024] FIGS. 3 and 4 show line elements with coaxial parallel
arrangements of two helically corrugated bellows 1, 1c (FIG. 3) or
1, 1d (FIG. 4) with different diameters and substantially equal
size thread pitch h with the latter in the same direction, so that
the bellows are engaged in one another or telescoped. The joining
end 4a of the outer bellows 1 serves as one cylindrical joining end
of a thus constructed line element and an end 7b of a coaxial pipe
element 7 extending through the inner bellows 1c, 1d remote from
the joining end 4a of the outer bellows 1 serves as the other
cylindrical joining end 4a of the line element. The end 7a of the
pipe element 7 near to the joining end is firmly connected by means
of a weld 9 to the end 3a of the inner bellows 1c, 1d near to the
joining end 4a of the outer bellows 1.
[0025] The remote joining end 3b of the inner bellows 1c is, as
shown in FIG. 3, connected by means of a connecting element, e.g. a
metal ring, firmly to the other joining end 4b of the outer bellows
1 by welds 5. The internal diameter of the outer bellows 1 is
larger than the external diameter of the inner bellows 1c.
[0026] According to FIG. 4 the internal diameter of the outer
bellows 1 is smaller than the external diameter of the inner
bellows 1d, the bellows helixes engaging in one another. In this
case the cylindrical joining end 3b of the inner bellows 1d can be
directly fixed, e.g. by welds 5, to the joining end 4b of the outer
bellows 1.
[0027] If now e.g. joining end 4a of outer bellows 1 is twisted,
there is a translatory axial displacement of the connection point 5
of the bellows, because the helically corrugated bellows 1
transforms the torsional movement into a length change, e.g. into a
shortening. For compensating this shortening, the inner bellows 1c
(FIG. 1) or 1d (FIG. 2) having a thread pitch in the same direction
lengthens, so that only the connection point 5 of the bellows, but
not the joining end 7b of the line element moves axially and
torsionally and consequently no coupling of torsional movements and
translatory movements takes place in the axial direction on the
line end 7b.
[0028] Whilst the arrangement shown in FIG. 4 has a higher
torsional stiffness due to the friction occurring with a relative
movement of the bellows 1, 1d, the arrangement shown in FIG. 3 acts
in a more torsion-soft manner and in this case one of the bellows
1, 1c can also be constructed as an annularly corrugated
bellows.
* * * * *