U.S. patent application number 12/190969 was filed with the patent office on 2008-12-11 for pipe extrusion plant.
This patent application is currently assigned to Krauss-Maffei Kunststofftechnik GmbH. Invention is credited to Herbert ULRICH.
Application Number | 20080305198 12/190969 |
Document ID | / |
Family ID | 33482238 |
Filed Date | 2008-12-11 |
United States Patent
Application |
20080305198 |
Kind Code |
A1 |
ULRICH; Herbert |
December 11, 2008 |
PIPE EXTRUSION PLANT
Abstract
A pipe extrusion plant for producing pipes with a variable
diameter includes an extruder, an adjustable calibration device,
and a cooling device, whereby a pipe to be produced is guided at
least in part during the production process. In order to be able to
provide a guide that is suited to different pipe diameters, a roll
assembly is provided to include a row of rolls which are placed one
behind the other in a take-off direction, with each roll mounted in
a bracket and supported to allow vertical positioning thereof in
dependence on the pipe diameter.
Inventors: |
ULRICH; Herbert;
(Muenster/Emsdetten, DE) |
Correspondence
Address: |
Henry M. Feiereisen;Henry M. Feiereisen, LLC
Suite 1501, 708 Third Avenue
New York
NY
10017
US
|
Assignee: |
Krauss-Maffei Kunststofftechnik
GmbH
Munchen
DE
|
Family ID: |
33482238 |
Appl. No.: |
12/190969 |
Filed: |
August 13, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11287938 |
Nov 28, 2005 |
7426843 |
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12190969 |
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PCT/EP2004/004361 |
Apr 24, 2004 |
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11287938 |
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Current U.S.
Class: |
425/112 |
Current CPC
Class: |
B29C 48/355 20190201;
B29C 48/90 20190201; B29C 2948/92123 20190201; B29C 48/913
20190201; B29C 48/92 20190201; B29C 48/09 20190201; B29C 48/9115
20190201; B29C 48/907 20190201; B29C 2948/92428 20190201; B29C
48/903 20190201; B29C 48/905 20190201; B29C 48/919 20190201 |
Class at
Publication: |
425/112 |
International
Class: |
B21C 3/00 20060101
B21C003/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 28, 2003 |
DE |
103 24 187.6 |
Claims
1. A pipe extrusion plant for producing pipes with different
diameter, comprising: an extruder for plasticizing a starting
material to produce a melt strand; an adjustable calibration device
sizing the melt strand to shape for forming a molten tube; a
cooling device for cooling the tube; and a roll assembly for
guiding the tube during advance through the calibration device and
the cooling device, said roll assembly including a plurality of
rolls arranged behind one another in a travel direction and
constructed to have at least two different roll geometries, and
adjustment means for automatically positioning the rolls in
vertical direction in dependence on a diameter of a pipe being
produced.
2. The pipe extrusion plant of claim 1, wherein the adjustment
means are constructed to carry out the positioning of the rolls in
dependence on a weight load upon the rolls.
3. The pipe extrusion plant of claim 1, wherein one of the rolls
has a first roll geometry to conform to a maximum radius of a pipe
being produced, and wherein another one of the rolls has a second
geometry to lateral support a smallest pipe to be produced.
4. The pipe extrusion plant of claim 2, wherein each of the rolls
is supported by an axle, said adjustment means including an elastic
element for movably supporting the roll so as to allow the roll to
move downwards as a load on the roll increases.
5. The pipe extrusion plant of claim 4, wherein the elastic element
is a spring.
6. The pipe extrusion plant of claim 5, wherein the spring is a
spiral spring.
7. The pipe extrusion plant of claim 1, wherein the adjustment
device includes a sensor for scanning a pipe diameter, and a drive
unit for vertically adjusting the rolls in response to a signal of
the sensor commensurate with the ascertained pipe diameter.
8. The pipe extrusion plant of claim 7, wherein the sensor is a
laser or mechanical sensor.
9. The pipe extrusion plant of claim 7, wherein the drive is an
electric drive, hydraulic drive, or pneumatic drive.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application is a divisional of prior filed copending
U.S. Application Ser. No. 11/287,938, filed Nov. 28, 2005, the
priority of which is hereby claimed under 35 U.S.C. .sctn.120, and
which is a continuation of prior filed copending PCT International
Application No. PCT/EP2004/004361, filed Apr. 24, 2004, which
designated the United States and on which priority is claimed under
35 U.S.C. .sctn.120 and which claims the priority of German Patent
Application, Ser. No. 103 24 187.6, filed May 28, 2003, pursuant to
35 U.S.C. 119(a)-(d).
[0002] The contents of U.S. application Ser. No. 11/287,938,
International Appl. No. PCT/EP2004/004361, and German Appl. No. 103
24 187.6, are incorporated herein by reference in its entirety as
if fully set forth herein.
BACKGROUND OF THE INVENTION
[0003] The present invention relates to a pipe extrusion plant for
production of pipes with adjustable diameter.
[0004] Nothing in the following discussion of the state of the art
is to be construed as an admission of prior art.
[0005] Pipe extrusion plants are generally known. The production of
plastic pipes involves initial melting of a plastic starting
material in an extruder and discharge via a pipe die. The exiting
thermoplastic molten tube from the pipe die is cooled under shape
constraint and calibrated. Calibration is of great importance as
far as pipe dimensions and tensions in the pipe wall are concerned.
Plastic pipes are calibrated predominantly on the outside, whereby
a vacuum calibration device is typically employed.
[0006] The still soft molten tube is drawn shortly after discharge
from the die through a calibrator which is mounted in the vacuum
tank. This calibrator can be configured as sleeve-type calibrator
or disk-type calibrator depending on the thermoplastic material.
The required contact pressure upon the calibrator is realized by
the pressure differential between the normal pressure inside the
pipe and the vacuum in the vacuum tank. The vacuum calibration
device includes a vessel which can be sealed vacuum-tight and may
be equipped preferably as cooling basin with spray nozzles. In and
following the calibration path, the extruded pipes must be cooled
down to such a degree as to be sufficiently stable in shape for
subsequent loads (for example take-off device, winder). Cooling of
the pipes may hereby be carried out in tanks with water baths or
spray nozzles.
[0007] Heretofore, the production of plastic pipes with varying
wall thicknesses or outer diameters required the availability of
different calibration devices. As a result, the respective parts
(e.g. calibrator) must be exchanged, necessitating a shutdown of
the machine and causing downtimes.
[0008] German Offenlegungsschrift DE 198 43 340 C2 discloses an
adjustable calibration device for different pipe dimensions. This
calibration device includes a plurality of lamellae which are
distributed in spaced-apart relationship about the circumference on
the outer side of the pipe to be calibrated. Viewed in travel
direction of the pipe, a plurality of such lamellae rims are
arranged within a calibrating station, with gaps being provided
between the individual lamellae of the individual lamellae
rims.
[0009] The vacuum tank and the spray baths must be provided with
guides to support the pipes. To date, commercially available
installations use rolls and support disks to meet this task.
Support disks, which have the desired pipe radius on the side
facing the pipe, are normally used in the vacuum tank. The use of
such support disks appears necessary because the pipe is still very
unstable in this early phase and has a tendency to assume an oval
shape without this guiding aid.
[0010] A drawback of a tube extrusion plant allowing the production
of pipes with different diameter is however the need to also change
the pipe guidance during each diameter change and the need to
manually conform or exchange the guides. As the center line of a
pipe should remain essentially the same for different pipes, rolls
for greater pipes must be arranged lower, while rolls for smaller
pipes must be elevated.
[0011] German Pat. No. DE 196 45 832 C1 discloses an apparatus for
guiding extruded components, especially pipes, including a
parallelogram of mountings on which rotatably supported rolls can
be adjusted so as to enable a continuous centered guiding of pipes
with varying diameters.
[0012] It would therefore be desirable and advantageous to provide
an improved pipe extrusion plant to obviate prior art shortcomings
and to allow automatic adjustment of a pipe guidance to adapt to
varying pipe diameters in a simple manner while yet properly
supporting the pipe during production and maintaining the pipe
substantially centered.
SUMMARY OF THE INVENTION
[0013] According to one aspect of the present invention, a roll
assembly for guiding a pipe in a pipe extrusion plant for producing
pipes of different diameter, includes a bracket, a roll supported
by the bracket, and an adjustment device for automatically
positioning the roll in vertical direction in dependence on a
weight load upon the roll.
[0014] The present invention resolves prior art problems by so
constructing a roll as to adjust its vertical position in
dependence on the weight load acting on the roll. Hereby, the
invention is based on the recognition that pipes of greater
diameter normally have a greater weight per meter. Thus, when the
roll is loaded by a pipe of greater weight, and thus normally also
of greater diameter, the roll moves further downwards than would be
the case, when the weight load on the roll is smaller as a result
of a smaller pipe and thus of smaller weight. Thus, when being
exposed to a smaller pipe, the roll moves upwards in opposite
direction. In this way, the center line for pipes of different
diameter can still be maintained at substantial same vertical
height in a simple manner.
[0015] The roll is rotatably mounted on an axle which is supported
indirectly or directly by an elastic element that forms the
adjustment device. A plurality of materials and devices known per
se may be used as elastic element, such as, e.g., rubber-like
elements. Currently preferred is the use of a spring, in particular
a spiral spring, as elastic element, for movably supporting the
axle so as to allow the roll to move downwards as a load on the
roll increases. Suitably, the spiral spring has a spring hardness
which is suited to a weight per meter range of the pipe which range
correlates with the dimension range. Thus, the roll for guiding the
pipes aligns itself spontaneously to the weight load.
[0016] According to another feature of the present invention, the
roll assembly includes a plurality of such rolls which are arranged
in succession, whereby the rolls may have varying roll geometries.
For example, rolls may be used which correspond to a maximum pipe
radius. The rolls may also be constructed in such a way as to
laterally support also the smallest pipes to be produced. Such
pipes are preferably arranged in the area of the vacuum tank. The
subsequent spray baths may use roll geometries which are configured
in the form of a double-V-block so that the pipe is guided also in
this case always on both rear sides.
[0017] According to another aspect of the present invention, a pipe
extrusion plant for producing pipes with different diameter
includes an extruder for plasticizing a starting material to
produce a melt strand, an adjustable calibration device sizing the
melt strand to shape for forming a molten tube, a cooling device
for cooling the tube, and a roll assembly for guiding the tube
during advance through the calibration device and the cooling
device, wherein the roll assembly includes a plurality of rolls
arranged behind one another in a travel direction and constructed
to have at least two different roll geometries, and an adjustment
device for automatically positioning the rolls in vertical
direction in dependence on a diameter of a pipe being produced.
[0018] By providing rolls of varying roll geometries, different
support functions can be realized and varying support lines can be
provided, for example a support of the pipe in the bottom area and
various side areas. For example, one of the rolls may have a first
roll geometry to conform to a maximum radius of a pipe being
produced, and another one of the rolls may have a second geometry
for lateral support of a smallest pipe to be produced.
[0019] According to another feature of the present invention, the
adjustment device may be constructed to carry out the positioning
of the rolls in dependence on a weight load upon the rolls. The
adjustment device may hereby be implemented by an elastic element,
such as a spring, e.g. spiral spring. Of course, other devices may
be conceivable as well for adjusting the rolls in their vertical
height. For example, the pipe diameter may be scanned by means of a
sensor (e.g. laser, mechanical sensor, etc.), and a drive may be
provided for the rolls (either a drive per roll or a drive for
several rolls respectively) for adjusting the rolls--in dependence
on the scanned diameters--in an automatic manner. Electric,
hydraulic or pneumatic drives may be used as drives. However, such
a control system is significantly more complex compared to the use
of a spring as adjustment device because of the need for a sensor,
an actuator and a control, and is thus applicable primarily, when
high precision is required.
BRIEF DESCRIPTION OF THE DRAWING
[0020] Other features and advantages of the present invention will
be more readily apparent upon reading the following description of
currently preferred exemplified embodiments of the invention with
reference to the accompanying drawing, in which:
[0021] FIG. 1 shows a schematic illustration of a pipe extrusion
plant having incorporated the subject matter of the present
invention;
[0022] FIG. 2 shows a schematic plan view of one embodiment of a
roll assembly according to the present invention installed in the
pipe extrusion plant;
[0023] FIG. 3 shows a schematic side view of the roll assembly of
FIG. 2;
[0024] FIG. 4 shows a perspective view of another embodiment of a
roll assembly according to the present invention for installation
in a pipe extrusion plant; and
[0025] FIG. 5 shows a schematic perspective view of yet another
embodiment of a roll assembly according to the present invention
for installation in pipe extrusion plant.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0026] Throughout all the Figures, same or corresponding elements
are generally indicated by same reference numerals. These depicted
embodiments are to be understood as illustrative of the invention
and not as limiting in any way. It should also be understood that
the drawings are not necessarily to scale and that the embodiments
are sometimes illustrated by graphic symbols, phantom lines,
diagrammatic representations and fragmentary views. In certain
instances, details which are not necessary for an understanding of
the present invention or which render other details difficult to
perceive may have been omitted.
[0027] Turning now to the drawing, and in particular to FIG. 1,
there is shown a schematic illustration of a pipe extrusion plant
generally designated by reference numeral 10. The pipe extrusion
plant 10 includes an extruder 12, arranged at the beginning of the
pipe extrusion plant 10 for receiving starting material which is
melted by the extruder 12 and discharged from the opposite end.
Melt produced in the extruder 12 advances subsequently through a
die 14 by which the melt is shaped to the required size. The die 14
is constructed as a variable die so that the exit gap can be
adjusted to the diameter and wall thickness requirements. Exiting
the die 14 is a thermoplastic tube which enters subsequently a
vacuum calibration device 16. The vacuum calibration device 16
includes a cooling basin which can be sealed vacuum-tight and in
which spray nozzles, not shown in more detail, are provided for
cooling the molten tube. Further provided in the vacuum calibration
device 16 is a calibration basket, also not shown in more detail,
for shaping the molten tube to final shape. The molten tube is
hereby pressed upon a disk-type calibrator as a consequence of the
pressure differential between the normal pressure inside the pipe
and the vacuum in the vacuum tank. The disk-type calibrator has
also a variable pipe geometry which is adjusted in correspondence
to set requirements for the diameter.
[0028] Following the vacuum calibration device 16, in which an
initial cool down already takes place, the tubular pipe advances
through a cooling device 18 where it is cooled down further by
means of water baths or spray nozzles to such a degree as to have a
stable shape that is maintained during subsequent processing and
exposure to loads. The cooling device 18 is followed by a take-off
device 20 by which the molten tube is drawn continuously and
without pressure and at even speed through the calibration device
16 and the cooling tanks. The take-off force of the plant has to
exceed hereby the encountered friction forces. An example of a
typical take-off device 20 is a caterpillar take-off unit.
Following the take-off device 20 is a separating device 22 for
cutting the tube to produce pipes of same lengths which are then
deposited on a delivery table 24 and from there are supplied to a
storage space.
[0029] Advance of the pipe through the vacuum calibration device 16
and the cooling device 18 requires the provision of a guidance of
the pipe. This is attained by the arrangement of a roll assembly
according to the invention which will be described hereinafter.
[0030] Referring now to FIG. 2, there is shown a first embodiment
of a roll assembly, generally designated by reference numeral 30,
which is simple in structure and essentially includes a roll 38
which is rotatably mounted on an axle 36. Opposite ends of the axle
36 are movably received in two aligned oblong holes 33 (FIG. 3),
which are formed in lateral legs of a U-shaped bracket 32 made of a
sheet metal bar which is bent twice to receive the U-shaped
configuration. The roll 38 has a surface geometry for properly
supporting the pipe. Secured to both upper ends of the bracket 32
are one ends of spiral springs 34 whose other ends are secured to
the axle 36. The springs 34 hold the axle 36 and thus the roll 38
in a substantial horizontal position at a level which is defined by
the spring force.
[0031] Both springs 34 expand depending on the load upon the roll
38, so that the axle 36 and thus the roll 38 moves downwards in
dependence on the weight load as applied by the pipe. The spring
hardness or spring constant is selected to take into account the
weight per meter range correlating with the dimension range. Thus,
the roll 38 moves downwards in response to the respectively
supported pipe such that the center line of the pipe is
substantially at same height, regardless of the diameter of the
pipe.
[0032] Through provision of the roll assembly 30, the pipe guidance
is automatically adjusted in a very cost-efficient manner and with
simple means to the differently selected diameters of a pipe to be
produced. Of course, adjustment to a weight per meter may also be
realized by exchanging the springs 34 or adding further elastic
devices (for example further springs).
[0033] It will be appreciated by persons skilled in the art that
the present invention is not limited to the arrangement of spiral
springs 34 as elastic elements in order to realize an automatic
positional adjustment of the rolls 38 in dependence on the pipe
being produced. As an alternative to spiral springs, other elastic
elements, such as leaf springs, rubber paddings etc., may be used
to allow a downward movement of the axle 36 in the oblong holes 33
in response to the weight load upon the roll 38.
[0034] Turning now to FIG. 4, there is shown a perspective view of
another embodiment of a roll assembly according to the present
invention, generally designated by reference numeral 30a for
installation in a pipe extrusion plant, depicted here by way of
example in the area of the cooling device 18 in opened state. Parts
corresponding with those in FIG. 2 are denoted by identical
reference numerals and not explained again. The description below
will center on the differences between the embodiments. The roll
assembly 30a is positioned immediately following the entrance of
the cooling device 18 and includes a bracket 50 for attachment of
one ends of two spiral springs 34 whose other ends are secured to
the axle 36 for movable support of the axle 36 and the roll 38.
Pipe 40 is shown here supported by the roll 38.
[0035] FIG. 5 shows another embodiment of a roll assembly according
to the present invention, generally designated by reference numeral
30b. The roll assembly 30b includes a bracket 52 and springs 54. A
first roll 56 is here supported by axle 36. The roll 56 has a
surface configuration which is constructed to allow support of a
maximal possible pipe radius on its lower side. The curvature of
the roll 56 in parallel relationship to the axle direction is thus
selected in accordance with the greatest pipe radius or a pipe to
be extruded. A second roll 58 is shown here to constitute a
substitute roll and has a surface geometry which differs form the
surface geometry of the roll 58 and is selected to allow lateral
support of a smallest pipe. As a consequence, a pipe 40 to be
extruded rests on the roll 58 at other contact points as on the
roll 56.
[0036] A pipe extrusion plant 10 according to the invention can
have a row of rolls arranged behind one another for establishing
the pipe guidance. It is hereby possible to use alternating rolls
of different surface geometry so that the pipe to be extruded can
be supported by varying line points. In this way, deformation of
the still fairly unstable molten tube as a result of its
instability can be avoided--in particular in the area of the vacuum
calibration device 16. It is no longer necessary to exchange
support disks during a diameter change and to replace them by
different rolls or support disk devices. The support disk function
is met in the present invention by the alternating use of rolls
with different surface geometry because different pipe portions can
be supported.
[0037] In summary, the present invention ensures that the position
of the guidance automatically conforms to the produced pipe
diameter. As a consequence, manual adjusting or exchange operations
are no longer needed. Of course, significantly more complex and
complicated lowerable or liftable guides are possible which are
covered by the scope of the present invention. For example, the
diameter or the weight of a pipe may be determined via a sensor and
the axle 36 of a roll 38 may be height-adjusted by a drive means in
correspondence to the weight of the axle 36. Conceivable are
electromotive or hydraulic drives for adjustment of the axle 36.
Such subject matter--also covered by the scope of the
invention--would be more cost-intensive compared to the embodiment
shown by way of example.
[0038] While the invention has been illustrated and described in
connection with currently preferred embodiments shown and described
in detail, it is not intended to be limited to the details shown
since various modifications and structural changes may be made
without departing in any way from the spirit of the present
invention. The embodiments were chosen and described in order to
best explain the principles of the invention and practical
application to thereby enable a person skilled in the art to best
utilize the invention and various embodiments with various
modifications as are suited to the particular use contemplated.
[0039] What is claimed as new and desired to be protected by
Letters Patent is set forth in the appended claims and includes
equivalents of the elements recited therein:
* * * * *