U.S. patent application number 15/513075 was filed with the patent office on 2017-10-12 for method and device for the production of an optimized neck contour on preforms.
The applicant listed for this patent is Mahir AKTAS. Invention is credited to Mahir AKTAS.
Application Number | 20170291334 15/513075 |
Document ID | / |
Family ID | 54883936 |
Filed Date | 2017-10-12 |
United States Patent
Application |
20170291334 |
Kind Code |
A1 |
AKTAS; Mahir |
October 12, 2017 |
METHOD AND DEVICE FOR THE PRODUCTION OF AN OPTIMIZED NECK CONTOUR
ON PREFORMS
Abstract
A method and device for producing an optimized neck contour on
preforms below the neck which is optimal for subsequent stretch
blow molding. The geometry has a significantly thinner wall
thickness than the neck itself. The preform can only be produced in
the injection molding tool, when axial channels are used on the
point or the vanes produce the thin points on the preform during
injection molding. The thin-walled geometry on the preform can be
produced outside of the mold during post-cooling by embossing. The
preform is there removed in a cooled receiving sleeve and is cooled
in the body by intensive contact cooling while no cooling contact
is made with the preform neck due to the initial position of the
embossing element. Due to the reheating of the neck they can be
mechanically deformed into a new geometry advantageous for blow
molding and thus wall thickness can be influenced.
Inventors: |
AKTAS; Mahir; (Balcova
Izmir, TR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
AKTAS; Mahir |
Balcova Izmir |
|
TR |
|
|
Family ID: |
54883936 |
Appl. No.: |
15/513075 |
Filed: |
September 21, 2015 |
PCT Filed: |
September 21, 2015 |
PCT NO: |
PCT/DE2015/000472 |
371 Date: |
March 21, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B29B 2911/1433 20150501;
B29B 2911/1402 20130101; B29L 2031/7158 20130101; B29B 2911/1404
20130101; B29C 45/0055 20130101; B29B 2911/14033 20130101; B29C
45/1773 20130101; B29C 45/4005 20130101; B29B 2911/14026 20130101;
B29C 49/4242 20130101; B29C 2045/7214 20130101; B29B 2911/14343
20150501; B29B 11/14 20130101; B29B 11/08 20130101; B29C 45/0081
20130101; B29C 49/06 20130101; B29K 2101/12 20130101; B29C 45/7207
20130101; B29C 49/6445 20130101; B29C 45/2632 20130101; B29C
45/2628 20130101 |
International
Class: |
B29C 45/00 20060101
B29C045/00; B29B 11/14 20060101 B29B011/14; B29C 45/72 20060101
B29C045/72; B29C 45/26 20060101 B29C045/26; B29C 45/40 20060101
B29C045/40; B29B 11/08 20060101 B29B011/08; B29C 45/17 20060101
B29C045/17 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 22, 2014 |
DE |
10 2014 014 144.6 |
Claims
1-21. (canceled)
22. A method for producing preforms with an improved neck geometry
beneath a threaded region or a transporting ring for a simplified
subsequent blow-molding process, wherein the produced preform made
of at least one thermoplastic material has a significantly thinner
wall thickness in a neck region beneath the thread than in the
thread itself, and the preform is provided in order to be formed
into blow-molded containers, the method comprising: providing at
least two channels having an increased wall thickness so that when
the preform is blow molded the holding pressure is maintained,
despite thin-walled regions, by the at least two channels with an
increased wall thickness, or integrating at least two slides in the
mold to produce the relatively thin wall thicknesses following an
operation of filling the cavities and a certain process time
period, or opening a mold once an outer skin of the preform has
solidified following initial cooling for a shortest period of time
possible; receiving the preforms from the open mold by a removal
arm and cooling sleeves of the removal arm; cooling the preform
stem, but not the neck region beneath the thread, by contact
cooling with the cooling sleeves; and carrying out an embossing
operation in which a plastically redeformable region is deformed
mechanically by embossing elements, in accordance with
repeatability necessary for further processing, by the plastic
material being embossed by cooling, pressing and pushing
operations, wherein a contour of the embossing elements is
configured, in combination with a supporting pin, so that said
contours are replicated in a reproducible manner on an open preform
to the greatest extent following the deforming operation.
23. The method according to claim 21, including providing all of
the preforms, as the preforms are being produced, with at least two
ribs or channels in the thin-walled region beneath the neck.
24. The method according to claim 21., wherein the channels for an
injection-molding solution arc configured so that, in order for a
holding pressure to be maintained, the plastic material in said
channels does not freeze any more quickly than the plastic material
in the preform neck.
25. The method according to claim 21, wherein, with embossing by
pushing, displacement of the plastic material is definable freely
in terms of time and is used for holding pressure, and slides
produce geometrically predefined ribs in a reproducible manner at
parting locations.
26. The method according to claim 21., wherein the embossing
operation displaces the plastic material axially into the cooling
sleeves so that lengthening of the preform is possible.
27. The method according to claim 21, including establishing a
temperature range between 90.degree. and 150.degree. at the preform
in the region where the embossing takes place.
28. The method according to claim 21, wherein embossing elements of
any desired number and size of a geometrically defined contour
deform the plastic material of the neck by pulling, pressing and
pushing the plastic mass until a volume between the two contours is
filled with the plastic material so that the geometry and the wall
thickness of the preform neck are defined in a repeatable
manner.
29. The method according to claim 21, wherein the embossing
operation is determinable freely in terms of time in each part of
the process.
30. The method according to claim 21, including, in a multi-cavity
application, individually setting an embossing force for each
cavity, by mechanical or pneumatic springs for each preform, in
order to ensure identical processes.
31. The method according to claim 21, wherein the embossing
elements are temperature-controlled or cooled to influence the
embossing operation,
32. The method according to claim 21, wherein the embossing
elements preform the preform neck for specific bottle-shaped
requirements, by pulling, pressing and pushing the plastic
material.
33. The method according to claim 21, wherein the embossing
operation is preceded by a waiting time of 1 to 20 seconds in order
to stabilize heat balance in the preform neck.
34. An apparatus for production of a preform with a geometry
beneath a neck that is optimized for a blow-molding process,
wherein the preform has a considerably thinner wall thickness in a
region beneath a thread than in the thread itself, the apparatus
comprising: a mold with at least one mold cavity for definitive
shaping of the preforms; an injection-molding apparatus that
plasticizes raw plastic material to introduce the plastic material
into the cavities with the closed mold under pressure, the mold
having channels or slides that ensure that a required holding
pressure is maintained in the neck despite the reduced wall
thickness, or the mold is responsible for the preform geometries in
a first shaping step; a removal arm, which is equipped with at
least one cooled cooling sleeve, equal in number to the number of
cavities, for removing the preforms, the cooling-sleeve having an
inner geometry that provides the preform stem, but not the region
of the preform neck, with contact cooling; and an embossing
apparatus that has embossing elements mounted in a radially
floating manner and use a cone to deflect an axial force
perpendicularly to an axis and to intensify said force to an extent
for an embossing operation that deforms the neck beneath the
threaded part by pulling, pressing and pushing operations, said
neck being defined by a cavity between the embossing elements and a
supporting pin so as to describe the contour and wall thickness of
the neck in a repeatable manner.
35. The apparatus according to claim 34, wherein the slide in the
mold is also movable under closing pressure.
36. The apparatus according to claim 34, wherein the embossing
elements are produced from rigid and thermally conductive
material.
37. The apparatus according to claim 34, wherein the embossing
elements are cooled or temperature-controlled.
38. The apparatus according to claim 34, wherein the cooling
sleeves are liquid-cooled.
39. The apparatus according to claim 34, wherein the embossing
elements are mounted resiliently with individually definable spring
forces.
40. The apparatus according to claim 34, wherein the embossing
elements are seated in a cone that serves as a uniform
force-transmitting element.
41. The apparatus according to claim 34, wherein each cooling
sleeve with embossing unit has an individual axial drive with
preselectable displacement length and forces.
42. The apparatus according to claim 34, wherein the preforms do
not have a supporting ring.
Description
[0001] Method and apparatus for the production of an optimized neck
contour on preforms.
[0002] The present invention relates to a method and an apparatus
for the production of preforms for forming an advantageous neck
geometry for the subsequent blow-molding process.
[0003] Preforms are injection-molded blanks which are made of at
least one thermoplastic material and are used in blow-molding
machines for producing stretch-blow-molded polymer-material
containers.
[0004] For the conventional production of preforms which is
described according to this invention, raw plastic material is
plasticized and then pressed under high pressure into a mold having
one or more cavities.
[0005] There are preforms according to FIG. 1 which, in geometrical
terms, comprise essentially a neck and stem region and a domed base
and are hollow on the inside as a result of a core being used in
the mold. The neck region is formed such that it can be configured
for reclosure for example by means of a screw cap. The neck region
must not undergo any further alteration above the transporting ring
during the blow-molding process, since otherwise there is a risk of
the closure system losing its complex capabilities, e.g. its
sealing function.
[0006] The region beneath the transporting ring, the adjoining stem
region and the domed base, in contrast, are inflated at elevated
temperatures to form hollow bodies, as a result of which the
plastic material is stretched and, in the process, solidifies to a
considerable extent. It is therefore the case that the preform
regions which are to be deformed are responsible in geometrical
terms, along with the core geometry, for the bottle quality which
is subsequently established.
[0007] It should be noted that, for an optimum result, the
temperature profile between the neck and the stem would have to
make an abrupt temperature jump of approximately 50-80.degree. C.,
although this is difficult to realize nowadays. In most cases, this
means, that as a result of a gradual temperature transition, the
material beneath the transporting ring cannot be optimally drawn
off into the bottle body during the stretch-blow-molding process,
and this results in unnecessary material consumption.
[0008] It is usually the mold which constitutes the highest level
of investment in a production system. It is therefore important for
the mold to be operated efficiently. Consequently, the preform, of
which the outer skin is in direct contact with the intensively
cooled mold steel, and therefore solidifies quickly there, is
demolded without sustaining damage or mechanical deformation, so
that the mold is ready for the next production cycle without any
time being wasted.
[0009] In the case of the conventional quick production cycles,
there is a considerable amount of residual heat remaining in the
interior of the preform wall, and this leads to reheating, as a
result of which the preform can soften again and crystallize, which
can render it unusable.
[0010] It is therefore imperative to continue with intensive
cooling of the preform, following demolding, in relatively
straightforward mold parts, so-called cooling sleeves, during a
number of production cycles.
[0011] The preform as is illustrated in FIG. 1 corresponds to the
current prior art, in the case of which it is inevitable for the
wall thicknesses of the preform, particularly in the region of the
domed base and of the stem, to be similar. If the material freezes
prematurely as a result of thinner wall thicknesses in the
injection region or in the neck region, it is not possible to avoid
shrinkage in the cooling phase as a result of the melt being
subjected to holding pressure, this having an effect on the entire
preform including the neck region, and this all consequently
results in undesired sink marks in critical regions of the preform,
particularly in the neck region.
[0012] The preform geometry as is shown in FIG. 2, the advantages
of which will be explained hereinbelow, therefore cannot be
produced by the known injection-molding method--or only if
appropriate measures are taken in order to maintain the necessary
holding pressure--since, for this invention, it is desired to have
a significantly thinner wall thickness in the region of the neck
beneath the transporting ring than in the following threaded
region, and it is therefore no longer possible to avoid sink marks
as a result of said thin region freezing prematurely.
[0013] The central object of the present invention is that of
describing a method and an apparatus which make it possible to
produce preforms with significantly more advantageous contours
beneath the transporting ring. The advantage resides in the fact
that the infrared heaters of the downstream blow-molding machines
can introduce heat energy more efficiently over this now enlarged
surface area with the simultaneously reduced wall thickness, in
order to bring the plastic material quickly to a temperature at
which it can be stretched. Therefore, during the operation of
heating the preform, more attention can be paid to the neck itself,
which must not be heated--the temperature jump from the cold neck
region to the hot preform body should be as abrupt as possible. It
is thus possible, during the stretch-blow-molding operation, to
draw out the material directly beneath the transporting ring in
optimum fashion to the benefit of the bottle body, which allows the
amount of raw materials used to be reduced.
[0014] A total of three solutions are proposed here for the purpose
of producing such preforms, said solutions being used either in the
mold itself or subsequently, during the post-cooling operation.
[0015] Therefore, as far as the first approach is concerned, it is
possible for example in the region of the mold to shape the preform
such that most of the neck-transition region is actually
thin-walled--but at least two or more channels are created, and
these channels do not freeze prematurely and therefore maintain the
holding pressure in relation to the neck. These channels are
manifested on the finished injection molding in the form of ribs,
which have no adverse effect on the subsequent blow-molding
operation--provided they are distributed as symmetrically as
possible over the circumference.
[0016] An alternative, second approach described here by the
invention is that of implementing, within the mold, at least two
slides, which, as far as possible at the end of the
holding-pressure phase, realize the thin contour beneath the
transporting ring when still in the injection mold. A favorably
selected timing would even result in the displacement process
assisting the holding pressure. This solution also produces ribs,
as a result of the parting locations of the slides; the number of
ribs is in direct proportion to the number of slides used. It is
possible, however, for said ribs to be significantly thinner than
the ribs which are necessary for the straightforward
injection-molding solution above, since the freezing of the melt in
the ribs is then no longer of any import.
[0017] A third approach for rendering the preform according to this
invention thin beneath the neck region can be realized during the
post-cooling operation and is based on the fact that there is
residual heat, which results in the preform softening again. In the
case of this solution using the post-cooling operation, where the
preforms removed from the mold basically soften again without
cooling as such being continued any further, i.e. they adjust to a
certain temperature level and are thus easier to deform again, the
desired contour can be introduced by embossing. While, as described
in the prior art, the preform stem and the preform dome are cooled
in the cooling sleeve by contact cooling, the region between the
preform stem and transporting ring then, as a result of the
cooling-sleeve function being modified, is excluded from the
cooling contact, as a result of which, at this location, a
temperature of approximately 90-130.degree. C. can be established
as a result of reheating and said location is thus deformable
again.
[0018] In contrast to the prior art, in the case of which the
preform is basically intensively cooled in order for a preform
which is generally solidified as far as possible to be obtained,
the basic idea of this part of the invention is that the modified
function of the cooling sleeve, which rules out direct contact with
the preform region beneath the transporting ring, precludes
intensive cooling there and thus allows for reheating. Following a
conditioning period of a few seconds, the preform region beneath
the transporting ring is at a temperature level at which it is most
easily deformable.
[0019] For the purpose of deforming the preform region beneath the
transporting ring, use is made of special embossing elements, which
form the new contour in a specific and reproducible manner.
[0020] The embossing elements, which are produced from solid
material, for example from tool steel, are arranged such that they
can apply high embossing forces as a result of straightforward
axial movement. Embossing is understood to mean that the plastic
material is deformed by pulling, pressing and pushing operations in
the manner predefined precisely by the embossing elements. A
further possible way of influencing the precision of the embossing
operation in said preform region is that of actively
temperature-controlling the embossing bodies.
[0021] The embossing operation can be understood, in principle, to
mean that the embossing elements press the soft plastic material
onto a hard cylinder, which rules out any inner deformation of the
preform. The plastic material therefore yields upward and downward,
as a result of which the preform can lengthen to an insignificantly
reproducible extent when the regions above and beneath the
embossing location are freely movable in the axial direction. It is
also the case that this method, in direct dependence on the number
of embossing parts, has slight ribs, since said embossing parts
have geometrical divisions in their contour which are replicated on
the preform neck. The embossing method has basically no influence
on the production-cycle time, since the time taken for injection
molding in the mold is longer than the embossing operation
itself.
[0022] The invention will be explained in more detail hereinbelow
with reference to the accompanying drawings, in which:
[0023] FIG. 1 shows a cross section of a preform as is
conventionally produced according to the prior art,
[0024] FIG. 2 shows a cross section of a preform in which the
region beneath the transporting ring has been configured using
different methods following or during the injection-molding process
in the mold, or in the post-cooling station, and the wall thickness
there can thus be decreased more or less as desired,
[0025] FIGS. 3-6 show schematic views of the post-cooling unit, in
which the embossing elements have been integrated and from which it
can be seen how the embossing forces can be applied,
[0026] FIG. 7 shows the schematic illustration, as seen from the
outside and from the side, of the flow paths on the wound-up
preform neck,
[0027] FIGS. 8a and 8b show the use of slide inserts for producing
relatively thin wall thicknesses in the mold following or during
the filling operation, and
[0028] FIG. 9 shows a plan view of an example of a production
arrangement for preforms.
[0029] The drawings are intended to assist the explanation
hereinbelow of the operation for producing the preform neck.
[0030] FIG. 1 shows a preform produced according to the prior art.
Said preform may have a transporting ring 3 for further
container-production steps--it may also be possible in the future,
however, to dispense with said transporting ring 3, since it is
possible, if appropriate, to grip the region between the ribs of
the preform. The wall thickness in the region beneath the
transporting ring 3 here has a similar wall thickness 12 as the
threaded region 15. On account of the risk of the melt freezing,
preforms according to FIG. 2, which are optimized for the
blow-molding process by having reduced wall thicknesses 9 beneath
the transporting ring 3, can be realized by injection molding only
with limited success, since it is then no longer possible for the
holding pressure, which counteracts the shrinkage of the preform
during the cooling process, to act in the critical regions.
[0031] This invention discloses three solution-related approaches
as to how the preform in FIG. 2 can be produced. It should be
mentioned here, however, that all three methods produce at least
two ribs or channels 14 on the circumference of the preform region
described, but said ribs or channels have no adverse effect on the
desired result. In order for it to be possible, however, for a
preform like that shown in FIG. 2 to be produced by conventional
injection molding, the mold 17 is configured such that at least
two, and even better three, channels 14 of sufficient width, as in
FIG. 7, are provided over the thin wall 9 beneath the preform neck
15, said channels ensuring that the holding pressure in the neck
region 15 is maintained.
[0032] In order to make the channels 14 narrower, however, it is
also possible for at least two sliding elements 13 to be integrated
in the mold 17, as illustrated in FIG. 8a and FIG. 8b, said sliding
elements then being used at the optimum point in time of the
injection-molding process. These elements press the still soft
polymer material in the mold into regions which are less critical
for the blow-molding process and, in doing so, possibly assist the
holding-pressure phase.
[0033] It is also possible, however, for narrower channels to be
achieved following the injection-molding process in that, following
initial cooling and opening of the mold 17, they are removed in a
conventional manner by a removal arm 18 and said modification is
shifted to the subsequent post-cooling phase. The removal arm 18
here has a multiplicity of cooling sleeves 8, in which the preform
according to FIG. 1 is introduced as far as the neck region 15.
[0034] Both the injection-molding machines with mold 17 and the
removal arm 18 are well known from the prior art.
[0035] Such a cooling sleeve 8 is illustrated in FIGS. 3 to 6. The
initially produced preform according to FIG. 1 has a conventional
shape with a relatively thick wall thickness in the region beneath
the transporting ring 3 and has its outer body region accommodated,
with a virtually full, direct contact, in a water-cooled cooling
sleeve 8. There is no need to give any more details relating to
this present cooling operation, which uses liquids or gases, since
numerous variants are known from the prior art.
[0036] The left-hand preforming position illustrated in FIG. 3
shows that the cooling sleeve 8, in the upper region, has embossing
elements 5, which are mounted on springs 6 and are secured by
screws. The preform 1 has its transporting ring 3 resting on the
embossing elements 5 and thus has not yet reached its axial end
position in the cooling sleeve 8. If the preform does not have a
transporting ring 3, it is then possible, as an alternative, for
the preform 1 to be brought into this position by a movable,
spring-mounted base support 11 on its domed base. In this position,
the embossing elements 5 are not yet in shaping abutment against
the preform 1, as a result of which this region can reheat on
account of contact cooling being absent. In order to intensify the
preform cooling, the number of cooling sleeves 8 may be a multiple
of the number of cavities in the mold 17. It is thus possible for
the residence time of the preform 1 or preform 2 in the cooling
phase to continue for a number of injection-molding cycles.
[0037] In order to prepare the mold 17 as quickly as possible for
the next injection-molding cycle, a removal arm 18 removes the
preforms from the mold region. The removal arm 18 here assumes such
a position that the mouth openings of the last-produced number of
preforms 1 are located opposite a transporting plate, on which are
mounted supporting pins 4 and bell-shaped pressure-exerting members
7 in a number equal to the number of preforms, can be aligned
axially. On account of the high level of force which is then
required, it is possible for the sake of simplicity for the
transporting plate to be mounted directly on the moving platen.
However, it could also be an independently movable unit.
[0038] The supporting pin 4 is provided essentially so that, when
the removal gripper 18 is brought together with the transporting
plate, the preform 1 is centered and, during the following
embossing operation by the embossing elements 5, deformation of the
internal diameter of the preform is for the most part avoided. The
embossing operation itself is initiated with the same action of the
removal gripper 18 being brought together with the transporting
plate, during which the embossing elements 5 are subjected to the
necessary force by way of the bell-shaped pressure-exerting element
7. The actual embossing forces are produced by the conical mounting
of the embossing elements 5, which thus move by a geometrically
predefined displacement amount in relation to the preform axis.
[0039] The angle and the length of the cone are selected in
accordance with the amount of force required for embossing
purposes.
[0040] The force and the point in time for the actual embossing
operation can be defined by a dedicated overall drive of the
transporting plate. If the transporting plate, however, is
connected directly to the moving platen of the injection-molding
machine, it is necessary to use individual axial drives if the
point in time for the embossing operation is to be delayed.
[0041] During removal, the preforms according to FIG. 1 are mounted
in the inner contour of the cooling sleeve 8 such that, although
they are indeed capable of executing a further defined-length axial
displacement, which is necessary for the following embossing
operation, they are prevented from so doing by the embossing
elements 5, since the transporting rings 3 rest there. If the
preforms do not have any transporting rings 3, then the preform is
preferably retained in this defined position by a movable,
resiliently mounted base supports 11. This defined residual axial
displacement is executed for the embossing operation by the
supporting pin 4, the bell-shaped pressure-exerting member 7, the
preform 1 and the embossing elements 5, counter to the restoring
compression spring 6. In the case of preforms without supporting
rings 3, the base support 11 is additionally moved counter to the
compression spring 10. The embossing displacement is executed
ideally when the heat balance is optimum for embossing as a result
of the reheating at the embossing location 9.
[0042] The embossing elements 5 can be formed, and positioned, in
more or less any desired manner in the shaping region. It is
possible for the embossing elements 5 to be all the same size or
different sizes. The number of embossing elements can also be
selected as desired on an individual basis. An ideal scenario is
that where there are three to six equal-size embossing elements 5,
which can each leave behind axial ribs 14 at the location where the
preform 2 is embossed. If these ribs 14 are distributed uniformly,
which is achieved by equal-size embossing elements 5, the
subsequent blow-molding process is not disadvantaged.
[0043] Once the embossing operation has been completed, the system
can be relieved of loading, as a result of which the restoring
compression spring moves the embossing elements 5, and thus the
preform 2, the bell-shaped pressure-exerting member 7 and the
supporting pin 4, into the starting position again. It is, of
course, possible for the restoring compression spring 6 to be
replaced by a pneumatic function, in which case the preform 2 can
be ejected at any desired later point in time via the embossing
elements 5. This is critical, in particular, if the preform, for
further post-cooling purposes, is to remain with contact cooling in
the cooling sleeve 8. In the case of a preform which has no
supporting ring 3, it is always possible for the embossing elements
5 to be relieved of stressing, since the preform in this case is
not moved axially.
* * * * *