U.S. patent application number 10/980635 was filed with the patent office on 2005-03-24 for plasticizing barrel lined on the inside with a coating, and method of making such a plasticizing barrel.
Invention is credited to Wurtele, Martin, Zellerohr, Michael.
Application Number | 20050064059 10/980635 |
Document ID | / |
Family ID | 27618697 |
Filed Date | 2005-03-24 |
United States Patent
Application |
20050064059 |
Kind Code |
A1 |
Zellerohr, Michael ; et
al. |
March 24, 2005 |
Plasticizing barrel lined on the inside with a coating, and method
of making such a plasticizing barrel
Abstract
A plasticizing barrel for a plastics processing machine includes
a body having a hollow cylindrical configuration and defining an
axis; and a coating formed on an inner wall surface of the body and
including at least one groove extending in axial direction of the
body. The coating, e.g., a wear-resisting protective layer, may be
produced through centrifugal casting, whereby the grooves are
formed by projections of a negative mold inserted in the
hollow-cylindrical body.
Inventors: |
Zellerohr, Michael; (Kleve,
DE) ; Wurtele, Martin; (Friedberg, DE) |
Correspondence
Address: |
HENRY M FEIEREISEN, LLC
350 FIFTH AVENUE
SUITE 4714
NEW YORK
NY
10118
US
|
Family ID: |
27618697 |
Appl. No.: |
10/980635 |
Filed: |
November 3, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10980635 |
Nov 3, 2004 |
|
|
|
10361781 |
Feb 10, 2003 |
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Current U.S.
Class: |
425/200 |
Current CPC
Class: |
B29L 2009/005 20130101;
B22D 19/08 20130101; B22D 19/06 20130101; B29C 48/68 20190201; B29K
2995/007 20130101; B29C 48/6801 20190201; B29C 48/03 20190201; B29C
45/62 20130101 |
Class at
Publication: |
425/200 |
International
Class: |
B29C 047/36 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 14, 2002 |
DE |
102 06 169.6-16 |
Claims
What is claimed is:
1. A plasticizing barrel for a plastics processing machine,
comprising: a body having a hollow cylindrical configuration and
defining an axis; and a coating lining an inner wall surface of the
body and including at least one groove extending in axial direction
of the body.
2. The plasticizing barrel of claim 1, wherein the at least one
groove has a helical configuration.
3. The plasticizing barrel of claim 1, wherein the coating is a
wear-resisting protective layer.
4. A negative mold for carrying out a method of making a
plasticizing barrel for a plastics processing machine, comprising a
base body defining an axis and formed with projections extending in
direction of the axis, said base body defined by a diameter which
is smaller than an end inner diameter of a plasticizing barrel
lined on an inner wall surface with a coating.
5. The negative form of claim 4, wherein the base body with the
projections define an outer diameter which is smaller than the
inner diameter of the hollow-cylindrical body by twice a thickness
of the coating.
6. The negative mold of claim 4, wherein the base body has a
cylindrical configuration.
7. The negative mold of claim 4, wherein the projections have a
surface lined with at least one coating selected from the group
consisting of adhesion-reducing coating and wear-reducing
coating.
8. The negative mold of claim 4, wherein the projections extend in
axial direction of the base body and has, in the direction in which
the negative mold is removed from a hollow-cylindrical body, at
least a configuration selected from the group consisting of
increasing width in circumferential direction and increasing height
in radial direction.
9. The negative mold of claim 4, wherein the projections have a
helical configuration.
10. A negative mold for carrying out a method of making a
plasticizing barrel for a plastics processing machine, comprising a
cage defining an axis and including projections extending in
direction of the axis.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application is a division of prior filed copending U.S.
application Ser. No. 10/361,781, filed Feb. 10, 2003, which claims
the priority of German Patent Application, Serial No. 102 06
169.6-16, filed Feb. 14, 2002, pursuant to 35 U.S.C.
119(a)-(d).
BACKGROUND OF THE INVENTION
[0002] The present invention relates, in general, to a plasticizing
barrel, and to a method of making such a plasticizing barrel.
[0003] Plasticizing barrels are used to plasticize granular plastic
material in an injection assembly or an extruder by means of a
screw for a subsequent injection process. As the inner wall of the
plasticizing barrel is subject to great stress during plasticizing,
it has been commonly proposed to line the inner wall with a
wear-resisting coating. The application of such a wear-resisting
coating may be implemented by a so-called centrifugal casting
process in which metallic powder is introduced into a rotating hot
hollow-cylindrical body, pressed against the inner barrel wall as a
consequence of centrifugal forces, and melted there. After a
cool-down period, the thus produced layer on the inside wall
exhibits a fairly good surface quality and requires only little
finishing works.
[0004] When more powerful plasticizing units are involved, barrels
with grooves are required whereby the grooves extend almost over
the entire length of the plasticizing barrel. These barrels do not
have a wear-resisting protective layer; rather, barrel blanks are
formed in "soft state" with the grooves, and subsequently the inner
barrel wall is hardened by a nitriding process.
[0005] It is also known to place so-called grooved bushings in the
feed zone of plasticizing units for improving the transport of
introduced raw plastic material. These grooved bushings are
normally also coated for wear-resistance, e.g., through a
high-temperature isostatic pressing process. The wear-resisting
protective layer of the grooved bushing can be provided either
directly into the plasticizing barrel, or the grooved bushing can
be produced separately and subsequently placed into the
plasticizing barrel. This process is applicable only for relatively
short grooves.
[0006] It would therefore be desirable and advantageous to provide
for a plastics processing machine an improved plasticizing barrel
which obviates prior art shortcomings and which includes an inner
coating and exhibits on its inner wall a groove or grooves.
[0007] It would also be desirable and advantageous to provide an
improved method of making such a plasticizing barrel.
SUMMARY OF THE INVENTION
[0008] According to one aspect of the present invention, a
plasticizing barrel for a plastics processing machine includes a
hollow cylindrical body, and a coating which lines an inner wall
surface of the body and is formed with at least one groove
extending in axial direction of the body.
[0009] The present invention resolves prior art problems by forming
the groove or grooves completely in the inner coating itself rather
than in the hollow cylindrical body. Suitably, the provision of the
groove in the inside coating can be realized by a centrifugal
casting process, whereby an axially extending negative mold, formed
with axial projections, is placed in the hollow-cylindrical body,
and, after carrying out the centrifugal casting process, is removed
again. According to an alternative process, the centrifugal casting
process may also be carried out in two stages by initially applying
a smooth layer on the inner wall of the hollow cylindrical body
through centrifugal casting in the absence of a negative mold, and
subsequently carrying out the centrifugal casting process with the
negative mold. The negative mold may be held in axial centered
disposition in the hollow-cylindrical body. However, this centering
step may be omitted altogether, when the initial smooth layer is
applied at very exact dimensions so that the negative mold is
already in centered disposition, when placed into the
hollow-cylindrical body.
[0010] A smoothest possible surface of the areas between the
grooves may be realized when the layer has a thickness which is
smaller than the height of the projections in radial direction. In
the two-stage process described above, the smooth inner layer may
be honed in the regions in which the projections are situated so as
to realize smooth groove bases in a simple manner. Of course, the
entire inner coating may be honed as well.
[0011] According to another aspect of the present invention, a
negative mold for use in a method of making a plasticizing barrel
for a plastics processing machine, may include a base body formed
with axial projections and defined by a diameter which is smaller
than an end inner diameter of the coated plasticizing barrel. The
base body may be cylindrical, and the projections may be part of a
cage.
[0012] According to another feature of the present invention, the
projections may be coated with an adhesion-reducing layer and/or
wear-reducing layer to facilitate a removal of the negative form.
As an alternative, it is, of course, also conceivable to so
configure the projections in the direction in which the negative
mold is removed from the coated hollow-cylindrical body as to have
increasing width in circumferential direction and/or increasing
height in radial direction.
[0013] According to another feature of the present invention, the
projections may have a helical configuration. As a consequence, the
negative mold can then be withdrawn from the hollow-cylindrical
body through a twisting motion.
BRIEF DESCRIPTION OF THE DRAWING
[0014] 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:
[0015] FIG. 1 is a schematic, cross sectional view of a
plasticizing barrel according to the present invention;
[0016] FIG. 2 is a schematic, cross sectional view of a negative
mold according to the present invention;
[0017] FIG. 3 is a schematic, cross sectional view of the
hollow-cylindrical body with inserted negative mold for making the
plasticizing barrel of FIG. 1;
[0018] FIG. 4 is a schematic, cross sectional view of the
hollow-cylindrical body with inserted negative mold and
introduction of material into the hollow-cylindrical body at a
process stage before centrifugal casting;
[0019] FIG. 5 is a schematic, cross sectional view of the
hollow-cylindrical body with inserted negative mold after
centrifugal casting;
[0020] FIG. 6 is a schematic, cross sectional view of a
hollow-cylindrical body with negative mold in an intermediate step
of a variation of a method according to the present invention
[0021] FIG. 7a is a plan view of a cage for making a plasticizing
barrel according to the present invention;
[0022] FIG. 7b is a fragmentary, perspective view of the cage of
FIG. 7a;
[0023] FIG. 8 is a cutaway, sectional view of the negative mold
with projections lined with another layer;
[0024] FIGS. 9a, 9b show schematic views of modified configurations
of projections of the negative mold; and
[0025] FIG. 10 shows a schematic view of another variation of a
negative mold.
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.
[0027] Turning now to the drawing, and in particular to FIG. 1,
there is shown a schematic, cross sectional view of a plasticizing
barrel according to the present invention, generally designated by
reference numeral 1 and including a hollow-cylindrical body 10
having an inner wall lined with a coating 12, e.g. a wear-resisting
protective layer, which is formed with grooves 14.
[0028] Manufacture of the plasticizing barrel 1 according to the
present invention involves the use of a negative mold, as shown in
FIG. 2 and generally designated by reference numeral 20. The
negative mold 20 has a cylindrical base body 16 which is formed
with radial projections 18 about its perimeter. The projections 18
extend in axial direction along the surface of the base body 16 and
may jut out in straight configuration, i.e. in axis-parallel
relationship to the base body 16, or may have a helical
configuration, i.e. extending around the surface of the base body
16, as shown in FIG. 10. As indicated in FIG. 2, the base body 16
has a diameter which is smaller than an inner diameter D.sub.i of
the finished plasticizing barrel 1. The outer diameter of the
negative mold 20, i.e. the diameter of the inner circle which
connects the projection and outer surface is D.sub.i+2*h.sub.N,
wherein h.sub.N is the height of the groove to be provided. B.sub.N
represents the width of the projections 18, i.e. width of the
grooves to be provided.
[0029] The negative mold 20, shown in FIG. 2, is placed into the
hollow-cylindrical body 10 which has an inner diameter which is
greater than the inner diameter D.sub.i of the finished
plasticizing barrel 1 by twice the thickness of the finished
coating 12, as shown in FIG. 3. Subsequently, metal powder 22 or
other liquid melt is introduced into the intermediate spaces
between the projections 18, as shown in FIG. 4. The
hollow-cylindrical body 10 with negative mold 20 and metal powder
22 is then subjected to a centrifugal casting process, i.e. the
hollow-cylindrical body 10 with negative mold 20 and metal powder
22 are heated and caused to carry out an axial rotation. As a
result, the metal powder 22 melts and lines the inner wall surface
of the hollow-cylindrical body 10 and migrates also into gaps 19
between the projections 18 and the inner wall surface, as shown in
FIG. 5 to form the coating 12. Subsequently, the negative mold 20
is removed from the hollow-cylindrical body 10 by being pulled out,
when straight projections 18 are involved, or by twisting, when the
projections 18 have a helical configuration. As a result of the
removal of the negative mold 20, grooves 14 are formed in the area
where the projections 18 have previously been situated, as shown in
FIG. 1. If need be, the inner contour of the plasticizing barrel 1
may be finished by honing (precision grinding).
[0030] Of course, the metal powder 22 or liquid melt may also be
introduced during the centrifuging process.
[0031] An alternative to the afore-described manufacturing process
of the plasticizing barrel 1 involves the application of a two-step
process to make the coating 12. As shown in FIG. 6, the inner wall
surface of the hollow-cylindrical body 10 is lined initially with a
coating 11, e.g. a wear-resisting protective layer, of constant
thickness, preferably, through centrifugal casting, with the
coating 11 having an inner diameter of D.sub.i+2h.sub.N.
Subsequently, the negative mold 20 or a cage carrying the
projections 18, is inserted in the interior of the
hollow-cylindrical body 10. An example of a suitable cage is shown
in FIGS. 7a and 7b and involves the arrangement of two end rings 30
(only one is shown here) between which the projections 18 are
secured. Thereafter, metal powder 22 is introduced into the
intermediate spaces between the projections of the negative mold
(or centrally into the hollow space of the cage), and the
hollow-cylindrical body 10 with coating 11 and the negative mold 20
are subjected to a further centrifugal casting process to form the
coating 12 with an inner diameter D.sub.i and with the grooves 14
in a manner described in conjunction with the previous embodiment.
Suitably, the areas of the initial coating 11 where the projections
18 are situated are honed, before the negative mold 20 or the cage
are placed into the hollow-cylindrical body 10 so that the finished
plasticizing barrel 1 has very smooth groove bases.
[0032] In this variation of the process according to the present
invention, the initial coating 11 is thick enough to allow the
projections 18 to automatically bear against the coating 11 so that
the need for a separate centering of the negative mold 20 or the
cage is eliminated.
[0033] The negative mold 20 or cage may be used repeatedly. After a
number of uses, finishing works, such as polishing, coating, may be
suitable.
[0034] Since the diameter of the base body 16 of the negative mold
20 is smaller than the inner diameter D.sub.i of the finished
plasticizing barrel 1, i.e. the groove height h.sub.N is smaller
than the height of the projections 18, the surface of the coating
12 between the grooves 14 is ensured to have a very even and smooth
configuration as a consequence of the centrifugal forces.
[0035] Depending on the stress the plasticizing barrel 1 is
subjected, various alloys may be used as protective layer. These
alloys are known to the person skilled in the art so that a
detailed description thereof is omitted for the sake of
simplicity.
[0036] As shown in FIG. 8, the projections 18 of the negative mold
or cage may be coated with an adhesion-reducing layer and/or
wear-reducing layer, as indicated by reference numeral 23. As an
alternative, it is, of course, also conceivable to configure the
projections 18 in the direction in which the negative mold 20 is
removed from the coated hollow-cylindrical body 16, indicated by
arrow 24, so as to have increasing width in circumferential
direction, as shown in FIG. 9a, and/or increasing height in radial
direction, as shown in FIG. 9b.
[0037] Although, centrifugal casting is a currently preferred
process to make a plasticizing barrel 1 according to the present
invention, other forming process may also be applicable, without
departing from the spirit of the present invention. Other forming
processes may involve, however, also different dimensioning of the
negative mold.
[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 their
equivalents:
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