Note: Descriptions are shown in the official language in which they were submitted.
BACKGROUND OF THE IN'VEN~.t'.'LODT
1. Field of the Invention
The present invention relates to a double-layer pipe
bend for a pipeline for transporting solids, particularly
concrete, to which liquids have been admixed. The pipe bend
includes a wear-resistant inner pipe and an outer pipe of
weldable material surrounding the inner pipe. Connecting
flanges at the ends of the pipe bend are welded to the outer
pipe. The outer diameter of the inner pipe and the inner
diameter of the outer pipe are selected in such a way 'that
the inner pipe can be inserted in the outer pipe without
deformation. An intermediate layer which supports the inner
pipe is provided between the outer pipe and the inner pipe.
2. Description of the Related Art
The magazine "MaschinenmarJct", wiirzburg, 84 (1978) 12
discloses on page 20U, Fig. 5 and in the left and center.
column on page 201 describing Fig. 5 a double-layer pipe bend
for a pipeline for transporting solids, particularly
concrete, to which liquids have been admixed, wherein the
pipe bend is composed of a lining element of artificial
basalt, of a thin-walled steel pipe surrounding the lining
element and connecting flanges at the ends which are
apparently welded to the steel pipe.
2
i~~~~~~i s~
The otater diameter of the lining element and the inner
diameter of the steal pipe are selected in such a way that
the lining element can be inserted in the steel pipe without
deformation. Zn additi.on, a mortar layer is provided between
the steel pipe and the lining element for supporting the
lining element in the steel pipe.
The pipe bend described above has the disadvantage that
it is difficult to mount the lining element in the steel pipe
by means of the hardening mortar because the mortar is
applied to the lining element hydraulically with a special
method which, however, is not described in detail.
The known pipe bend has the further disadvantage that,
due to the friction between the transported medium and the
lining element, the lining element can be displaced in axial
direction of a pipeline relative to 'the steel pipe. This
axial displacement of the lining element relative to 'the
steel pipe may then ~.ead to a mortise joint-type connection
between successive pipe bends or between a pipe bend and a
straight pipe. As a result, it is nearly impossible to
remove a pipe bend from a pipe line radially as it is
repeatedly required in practical operation. Even if the
requirement is met that several pipes can be removed from a
pipeline with at least one pipe bend although only the pipe
bend has to be removed, there still is the problem that
portions of the axially displaced lining elements project
3
freely axially beyond the steel pipes. These portions are of
a very sensitive material and, therefore, are extremely
susceptible to being damaged, particularly in view of the
fact that the pipe bend is subjected to high loads during
operation.
In addition, if there are several axially displaced
lining elements, it is possible that at the rearward end of
the displaced lining elements in conveying direction an
extremely wide gap is formed between a lining element which
has not yet been displaced and 'the next already displaced
lining element. Accordingly, in the area of the gap there is
the increased danger of turbulence of 'the transported medium
which, in turn, leads to extremely high wear.
The known pipe bend has the further disadvantage that
the wall thicknesses of the line element are the Name in all
areas. As a result, it is not possible to take into account.
the particular operating conditions of those pipe bends which
are located at the conveying end of a concrete conveying
arrangement which includes pipe sections with several bends,
such as, self-propelled concrete pumps. This is because
these pipe bends are subjected to strong impact-like loads by
the concrete which is transported through the pipe lines.
Consequently, these pipe bends have a significantly shorter
service life than the adjacent straight pipe sections.
4
German Offenlegungsschrift 33 15 819 discloses a
straight pipe element composed of an owter steel pipe and a
pipe of plastic material inserted in the steel pipe. The
annular gap between the plastic pipe and the outer steel pipe
is filled by a hardening filler material. In addition, a
flange is arranged at each end of the steel pipe. One end
of the plastic pipe is extended over a sleeve at the other
end of the steel pipe.
German patent 8 05 637 discloses a pipe bend far stowing
lines composed of three segments. Each individual segment
has a wearing insert of asymmetrical wall thickness which is.
supported by two housing halves of equal construction which
can be coupled to each other by means of snap closures. The
housing halves are to be made of light metal.
German Auslegeschrift 10 95 768 shows the connection
between two double-layer pneumatic stowing pipes. Z'he
material of the two layers is not cTescra.bed. It is also not
described how the inner layer can be inserted in the outer
layer without deformation.
CA 02048903 1997-07-04
SUMMARY OF THE INVENTION
Therefore, it is the object of the present invention
to improve a double-layer pipe bend of the above-described
type in such a way that its service life is significantly
extended while it can be used for a greater variety of
purposes and is less complicated to manufacture. In addition,
it is to be ensured that the pipe bend can be removed radially
without problem from a closed pipe line.
In accordance with the present invention, there is
provided a double-layer pipe bend for a pipeline for
transporting solids to which liquids have been admixed,
comprising: a wear-resistant inner pipe; an outer pipe of
weldable material surrounding the inner pipe; the inner pipe
having an outer diameter and the outer pipe having an inner
diameter, the outer diameter of the inner pipe and the inner
diameter of the outer pipe being selected such that the inner
pipe is insertable in the outer pipe without deformation;
connecting flanges at ends of the pipe bend welded to the
outer pipe, wherein the inner pipe has a length such that it
is axially fixed between the connecting flanges; an
intermediate layer which supports the inner pipe between the
outer pipe and the inner pipe, wherein said inner pipe is at
least partially embedded in said layer; a radially outer pipe
portion and a radially inner pipe portion on said pipe bend;
and a greater wall thickness in said outer pipe portion than
in said inner pipe portion, wherein said outer portion is
subjected to a higher load by the mixture and said inner
portion is subjected to lower loads by the mixture.
- 6 -
23824-144
CA 02048903 1997-07-04
An important aspect of the present invention is the
fact that the inner pipe is now constructed relative to the
outer pipe in such a way that the transported medium,
particularly concrete, can itself serve to protect the inner
pipe. Thus,
- 6a -
23824-144
due to the gaps between the connecting flanges and the inner
pipe resulting from the dimensions of the inner pipe relative
to the outer pipe and to the connecting flanges, the
transported medium can reach between the inner pipe and the
outer pipe and, consequently, can form the pressure
compensating-layer for protecting the inner pipe. As a
result, the inner pipe is essentially embedded in the
transported medium. Consequently, independently of its
consistency, the transported medium flowing in the inner pipe
can no longer exert forces on the inner pipe which could lead
to cracks or even ruptures of the inner pipe. A pressure
compensation between the outer and inner surfaces of the wall
of the inner pipe is always present. Consequently, with the
exception of wear due to friction, the pipe wall is not
subjected to any additional harmful loads.
The selection of the material of the inner pipe now also
no longer constitutes a prob:l.em. Thus, 'the material of the
inner pipe can always be se~.ected in an optimum manner for
each type of use.
In addition, the wall thickness of the inner pipe,
particularly if made of cast steel, can now be specifically
adapted for each type of use. Accordingly, those portions
can be made.with greater thicknesses which are subjected to
greater wear because of the curvature of the pipe. These are
the points which are located radially farthest remote from
7
the center of curvature of the pipe bend. Consequently, it
is possible in an advantageous manner to reduce -the amount of
material used for the inner pipe depending on the type of
application.
Since the inner pipe is embedded in a pressure
compensating layer formed by the transported medium, the
inner pipe is mounted in such a way that it is free of
impact-type loads. Since the inner pipe is embedded in the
pressure-compensating layer, it is essentially only subjected
to the inner friction wear. Thus, the service life of a pipe
bend equipped with the inner pipe according to the present
invention and used as an end section of a pipeline for a
self-propelled concrete pump can be adapted to the service
life of the other pipeline sections which are subjected to
lower loads.
Finally, since the inner pipe is exactly fixed in the
outer pipe, it is easily possible to rad:La:Lly remove a pipe
bend from a pipeline and to mount a new pipe bend in the
pipeline.
Accordingly, all the features of the present invention
described above are necessary to obtain the effects mentioned
above.
8
In accordance with an advantageous further development
of the present invention, at least one of the connecting
flanges is composed of an outer coupling ring welded to the
outer pipe and of an inner wearing ring. A short axial
portion of the coupling ring of the connecting flange which
is otherwise arranged on the end faces of the outer pipe and
the inner pipe extends over and is welded to the outer pipe.
As a result, any unnecessary material for the connecting
flange is avoided, particularly for the coupling ring which
is of a weldable steel. In addition, centering of the outer
pipe and of the inner pipe in the axial portion of the
coupling ring is significantly simplified. Depending on the
type of use, one such connecting flange may be sufficient.
However, connecting flanges of 'this type may frequently be
useful at both ends.
The wearing ring may be fixed in the coup7.:ing ring in a
conventional manner, for example, by hardening it once or
several 'times. However, in accordance with another
advantageous feature of the present invention, the wearing
ring can also be embedded in a pressure-compensating layer
formed by the transported medium between the wearing ring and
the coupling ring and the wearing ring may be axially fixed
in its position by means of a radial undercut and/or a collar
on the coupling ring. Thus, the radial undercut and/or the
collar on the coupling ring and/or an the wearing ring serves
9
~~~~~n~
to fix 'the wearing ring axially, while the pressure-
compensating layer formed by the transported medium ensures
that the wearing ring is safely embedded in the coupling
ring.
In accordance with another feature of 'the present
invention, the connecting flange extends over the outer pipe
at least at one end of the outer pipe and is welded to the
end face of the outer pipe which faces toward the center of
the pipe, wherein the connecting flange extends with a radial
collar along the end face of the outer pipe and at least
partially over the end face of the inner pipe. Thus, the
inwardly directed narrow radial collar can extend along the
end faces of the outer pipe and of the inner pipe to the
inner diameter of the inner pipe. However, it is also
conceivable that the radial collar extends over the end face
of the outer pipe but in a recess on the circumference of the
inner pipe. The end faces of the radial collar and of the
inner pipe are then located in the same radial plane. Of
course, this type of construction can k~e provided on both
ends of tY~e pipe bend.
The various features of novelty which characterize
the invention are pointed out with particularity in the
claims annexed to and forming a part of this disclosure. For
a better understanding of the invention, its operating
advantages attained by its use, reference should be had to
the drawing and descriptive matter in which there are
illustrated and described preferred embodiments of the
invention.
BRIEF DESCRIPTION OF THE DRAWING
In the drawing:
Fig. l is a vertical longitudinal sectional view of an
end portion of double-layer pipe bend according to the
present invention;
Fig. 2 is a vertical sectional view of an end portion of
a second embodiment of the double-layer pipe bend according
to the present invention;
Fig. 3 is a vertical sectional view of an end portion of
a third embodiment of the double~layer pipe bend according to
the present invention;
Fig. 4 is a vertical sectional view of an end portion of
a fourth embodiment of the double-layer pipe bend according
to the present invention;
Fig. 5 is a vertical sectional view of an end portion of
a fifth embodiment of the double-layer pipe bend according to
the present invention.
12
DESCRIPTION OF TF~E PREFERRED EMBCDIMEF1TS
In Figs. 1-5 of 'the drawing, reference numerals 1 or 1a,
1b, 1c, ld denote a double-layer pipe bend for transporting
concrete. The pipe bend 1, 1a-1d as combined with other pipe
bends 1, 1a-ld or s'traigh't pipes to form a pipeline. Such a
pipeline with several bends is preferably used in so-called
self-propelled concrete pumps.
Each pipe bend 1, 1a-1d is composed of an inner pipe 2
of cast steel, of an outer pipe 3 of weldable material
surrounding the inner pipe 2) and of connecting flanges 4,
~a-4d at the ends which flanges are welded to the outer pipe
3.
The outer diameter of the i.nndr pipe 2 and the inner
diameter of the outer pipe 3 are selectec'i specifi.ca:Lly
relative to each other and the 2ength L of the inner pipe 2
between the connecting flanges 4, 4a-4d at the ends are
dimensioned in such a way that the previously processed inner
pipe 2 can be inserted into th.e outer pipe 3 without
deformation. Subsequently, the connecting flanges 4, 4a-~d
at the ends are slid at the end faces over 'the outer pipe 3
and are then welded thereto.
lz
Gaps axe formed between the outer pipe 3 and the inner
pipe 2. The concrete can travel through gaps Sp at the end
faces and, consequently, can form a pressure-compensating
layer 5 between the outer pipe 3 and the inner pipe 2. In
other words, in operation the inner pipe 2 is essentially
embedded in 'the pressure-compensating layer 5 and,
consequently, is subjected to the same pressures on the
inside and on the outside.
Figs. 1-3 of the drawing show embodiments in which the
connecting flanges 4, 4a, 4b are each formed by a outer
coupling ring 6, 6a, 6b welded to the outer pipe 3 and of an
inner wearing ring 7, 7a, 7b. The coupling rings 6, 6a, 6b
have short axial portions 8 with which they extend over the
outer pipe 3. The end faces of the portions 8 are welded to
the circumferential surfaces of the outer pipe 3.
In the embodiment of Fig. 1, the wearing rang 7 is
immovably fixed in the coupling ring ~ by hardening the ring
once or several times.
In the embodiment of Fig. 2, the wearing ring 7a is
embedded in a pressure-compensating layer 9 which can be
formed during operation from the coupling gap or from the gap
sp between the wearing ring 7a and 'the coupling ring 6a.
13
9
The coupling ring 6a has at the free end thereof an
inwardly directed radial collar 10 which engages in a
circumferential groove 11 of the wearing ring 7a) so that the
wearing ring 7a is axially fixed in this manner.
In the embodiment of Fig. 3, the coupling ring 6b has in
the vicinity ofc the portion 8 an undercut 12 which is engaged
by a radial collar 7.3 of the wearing ring 7b. In this
manner, the wearing ring 7b is axially secured in the
coupling ring 6b. It can also be seen that the concrete
between the coupling ring 6b and the wearing ring 7b can
build up during operation from the coupling gap or the gap Sp
a pressure~compensating layer 9 in which the wearing ring 7b
is essentially embedded.
Of course, it is conceivable that, if required, both
types of fastening of 'the wearing rings 7a, 7b according to
Figs. 2 and 3 can be used simultaneously.
The embodiments of Figs. ~ and 5 have cannect:ing flanges
4c, 4d without wearing rings. As can be seen in Fig. 4, the
connecting flange 4c which is of weldable steel has a
radially inwardly directed collar 14 which extends on the end
faces of the outer pipe 3 and the inner pipe 2. The inner
diameter of the connecting flange 4c corresponds to the inner
diameter of the inner pipe 2. The axial length of the
14
connecting flange 4c is a multiple of the width of the narrow
radial collar 14.
In the embodiment of Fig. 5, the narrow radial collar 15
of the connecting flange 4d extends radially in such a way
that it extends along the end face of the outer pipe 3, but
engages only in a circumferential groove 16 in the edge of
the inner pipe 2. The axial length of the connecting flange
4d is also a multiple of the width of the radial collar 15.
In the embodiment of Fig. 4 as well as in the embodiment
of Fig. 5, the end faces of 'the connecting flanges 4c, 4d
directed toward the longitudinal center of the pipe are
welded to the outer circumferential surfaces of the outer'
pipe 3.
Finally, Figs. 1-5 show that the thickness of the pipe
wall 17 of the inner pipe 2 in the radially outer pipe
portions relative to the center of curvature of the pipe
bends 1, 1a-1d is greater than 'the thickness of the pipe wall
17 in the radially inner pipe portions. Accordingly, it is
taken into account that the radially outer pipe portions are
subjected to substantially greater wear by the concrete than
are the radially inner pipe portions. The wall thickness may
also vary in axial direction of the pipe bends 1, 1a-1d in
dependence upon differently occurring loads.
i~'~'~~~~a~
while specific embodiments of the invention have
been shown and described in detail, to illustrate the
inventive principles, it will be understood that the
invention may be embodied otherwise without departing from
such principles.
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