Note: Descriptions are shown in the official language in which they were submitted.
~ 5
-- 1 --
This appllcation is a divi.sion of application
Serial No. 466,796, filed October 31, 1984.
I~e lnvention relates to a tubular pre-moulding
of a thermoplastic, suitable for subsequent shaping to
give containers by a blow-moulding process, and to a
process and eaAuipment for producing the pre-moulding.
~ a tube, future mouth parts and parts o~ adjacent neck
sections are moulded to pre-m~uldings, from two blank
parts joined to one another, by an axial stretch process
and a blow-moulding process, the parts in the transition
between the two mouth parts being severed in order to
form two separate blank parts which~ after closing at
one of the ends and subsequent reworking to produce the
re~uisite closing surfaces at the respective ~ther ends,
each alone form a tubular pre-moulding~
- Xn a production process used for the manufacture
of containers from a thermoplastic, blanks normally
called p~e-mouldings for containers are produced from
severed parts of extruded long tubes of an amorphous
thermoplastic. At one end, the severed pieces are
shaped in such a way that they form the future mouth part
of the container, whilst they are closed at the opposite
endO
~ he present invention eliminates certain disad-
vantages connected with the production process indicated
above, according to the known terhnology. ~X~
.. _ . . . _ . .. .
-- 2 --
The invention is suitable especially for the
manufac~ure of containers ~rom a thermoplastic of the
p~lyes-~er or polyamide type. Examples of such materials
are polye~hylene terephthalate, polyhexamethylene-
adipamide, polycaprolactam, polyhexamethylene-sebacamide,
polyethylene 2,6- and 1,5-naphthalate, polytetramethylene
1~2-dihydroxybenzoate and copolymers of ethylene
terephthalate, ethylene isophthalate and similar
.polymers. T~e description of the invention below
relates mainly to p~lyethylene terephthalate, called
-PET in the further text, but the invention is not
restricted only to the use of either this material or
one of the other materials already mentioned; instead,
it is also applicable to many other thermoplastics.
For a better understanding of the existing
.problem and of t~e invention, several characteristic
properties of the polyester polyethylene terephthalate
~re described below. From the literature, lor exam~le
Properties of Polymers, by D.W. van Krevelen, Elsevier
Scientific ~ublishing Company, 1976J it is known that the
properties of the material change when amorphous poly-
ethylene terephthalate is oriented. Some of these
changes are shown in the diagrams, Figures 14.3 and 14.4
on pages 317 and 31g in the book "Properties of Polymers".
The symbols used in the discussion oelow correspond to
- . the symbcls in the said bo~k.
- PET, like many other thermoplastî.cs, can be
~ oriented by stretc~ing the material. Nvrmally this
stretching takes place at a temperature abo-ve the glass
transiti~n temperature Tg of the material. The
strength properties of the material are improved by
orienting. The literature shows that, in the case of
~he thermoplastic PET, an increase in the stretching
ratio~ that is to say the quo~ient of the length of
the stretched material and the length of the unstretched
material, also leads to an increase in the impro~ement
of the material properties~ When the stretching ratio
J~ is increased from about 2 tu a little more than 3~
particularly large changes in the material properties
are obtained~ The strength in the direction of orien-
tation is here markedly improved, whilst at the same time
the density-~ and likewise the crystallinity Xc rises and
the glass transition temperature Tg is raised. It can
be seen from the diagram on page ~17 that3 a~ter stretch-
in~ with~ assuming the value of 3.1, the material with-
stands a force per unit area, which corresponds to ~ = 10
coupled with a very small elongation, whilst the elonga-
tion at~ 2.B is substantially larger. In the
further text, the term "step" is sometimes used to
designate orienting which is obtained by
stretching, or a reduction in thickness by about 3 times,
and which leads to the-marked improvements of the material
properties, indicated above.
The diagrams quoted above show changes which are
obtained on mono-axial orientation of the material.
In biaxial orientation, similar effects are obtained in
S
both directions of orienta~ion. - Orientation is
carried out as a rule by successive stretchings.
Improved material propertie.s, corresponding to
th~se which are obtained by the ~Istep~ defined above, are
also ~btained if an amorphous ma~erial is st~etched until
it ~lows and, before flowing, the material is at a tem-
perature which is below the glass transition temperature
Tg, In a rod being drawn9 a reduction of the diameter
of.about 3 times results in the flow zoneO On
drawingg the flow zone i5 continuously displaced into
the amorphous material, whilst at the same time the
material~ which has already undergone the state of
flowing, absorbs the tensile forces of the test rod
w;thout an additional permanent stretchingO
For bottlesS defined external diameters of the
mouth with the associated thread are standardised and, in
the technology known at present when using the moulding
.process described as an introduction, this determines the.
greatest diameter which is permissible in the blow
.moulded container body. The reasons for this are
explained in more detail in the following text. In
order to obtain an amorphous starting material for the
pieces of tube, which are to be shaped into pre-mouldings,
.~he material must be cooled rapidly to below the glass
transition temperature Tg after extruding - in ~he case
of ext~uded tubes from which the pieces of tube are
severed. In the case of excessive wall thickness, the
materi~l does not possess adequate heat conductîvity t~
, .
- 5
enable the central sect.ions of the wall ~o ~e cooled as
rapidly as required, so that the material located in the
centre becomes crystal~ine ancl opaqueO For this
reason 9 viewed theoretically, the largest possible wall
thickness of the extruded tubes.is less than about ~ mm.
In practice, however, wall thicknesses of less than 4 mm
are used as a rule. In fact, in blow-moulding of a
pre-moulding having wall material of excessive thickr.ess,
problems arise due to the cooling of the material during
the actual blow-moulding step and be~ore the material
reaches the wall of the mould. The blow-moulded con-
tainer is no longer clear as glass and, instead 9 contains
opaque white sections. In blow-moulding, in order to
obtain containers having the requisite resistance against
stresses and penetration o~.the container..wall, the wall
thickness of the finished container must not fall below a
defined value. Moreover, a reduction of the external
diameter of the tube during the shaping of the mouth part
of the pre-moulding is not possible in accordance with
known technology. The result is that the desired
mouth diameter of the blow-moulded container is decisive
for the diameter of the pre-moulding and thus for the
maximum diameter of the blow-moulded container body.
If bottles of large capacity are required, these bottles
are extended, according to known technology, in the axial
direction after they have reached the maximum possible
-diameter.-- In additiQn to the disadvantage of a certain
instability, the extension represents an unsatisfactory
utilisation of the quantity of material in the container
-- 6 --
body since the re~uisite quanlity of mate~ial per unit
volume of storage capacity is greater than would be
necessary if ~oth the diameter and the length of the
container body were adapted to the actual volume required.
Moreover, the unnecessarily large sur~ace of the con-
tainer leads to a corresponding increase in the overall
penetration of carbon dioxide during the storage of
beverages containing carbonic acid.
To utilise the material properties of the material
in the best way, it is desirable that the diameter of
those parts of the pre-moulding which, after the blow-
moulding step, represent the actual container body, is
given a value which has the result that the material in
the blow-moulded container body assumes the desired
orientation. In containers of PET it is desirable
that the material, in conjunction with blow-moulding7 is
biaxially stretched in such a way that the product of the
stretchings is about 9.
The above shows that, according to known teoh-
nology, the quantity of material in the mouth part is not
determined by the calculated stresses but by the maximum
diameter of the container body. As a rule, this leads
to a considerable excess of material in the mouth part.
For example, in a PET bottle of 1 litre capacityy
the mouth part can, according to known technology, contain
up to 25-30% of the total ~uantity of ~aterial. Dis-
regarding the unpl-easant appearance of the oversizing sf
the mout~ part, this fact also results in a waste of
material, which i5 of importance in the mass production
s
-- 7 --
of articles.
. In the technology applied at present, the m~uth
part and adjacent neck partsconsist of unoriented material,
that is to say amorphous matlerial. This means that the
material in the mouth par~ including the adjacent neck
parts has properties which differ from those of the con-
tainer body. In containers of, for example, PET, the
material in the mouth part has a glass transition tem-
perature Tg of 71C, whilst the glass transition tempera-
ture ~f the material in the container body is about 81C.
It follows from this that the material in the mouth part
so~tens at a lower temperature than the material in the
container body.
It is already known, by cold-forming of the m~uth
part of the blank, to displace material downwards ~rom th~
mouth part into the sections of the blank, which later
represent the wall sections of the container body. In
this way, a certain matching of the quantity of material
in the mouth part to the ~uture stresses is achieved but,
between the actual container body and the mouth part 5
neck sections are formed in which the material is stre~ched
by a factor of less than 3. These neck sections in the
moulded container thus consist of inadequately oriented
material, whilst at the same time the wall thickness is
undesirably large. This metho~ is also known from Canadian
Application No. 322,4~9, filed Fëbruary 28, 1979, inventor,
Kjell M. Jakobsen. British Patent Specification 1,536,194
puhlished December 20, 1978 to Carnaud Total Interplastic has
disclosed a method wherein a tubular blank, which is closed
at one end and which is provided at the other ena with
` E3 --
beading for fixing the blank :in a downstream blowing
element, is injection-moulded and wherein the tubular
blank is blow-moulded after-a certain reshaping to give
a container. Material in the tubular part of the
blank is expanded in the radial direction at a temperature
abo~e tlle glass transition temperature Tg in order thus to
form the mouth part of the container. A container
~ormed in the manner described possesses a mouth part and
a neck section in which the material has been exposed to
only very slight s~retching and hence orienting, 50 that
the disadvantages, already indicated, with respect to the
mouth part of the known containers are also present in
this container.
The invention described in-Bri~tish Patent Specifica-
tion 1,536,194 also has the disadvantage that only a part of
the material content of th~ injection-moulded tubular blank
is utilised when reshaping the blank to give the finished
con~ainer. It is obvious that the losses of materiaL, ~ich
occur in this process, represent an economic disadvan'cage in
the mass production of articles.
From Federa~ German Of~enlegungsschrift DOS
2,540,930, published April 8, 1976, a process is known where-
in a tubular blank of PET is resha~ed to give a container and
wherein the container w~l consi~ts of a material which is
stretched by a factor of, for example, more than 1.5. The bottom
part o~ the container consists of an amorphous unoriented
material, whilst the neck sections of the container con-
sist of material which has been oriented only to a slight
extentO As a result of heating and crystallisation,
~ 5
caused thereby, the strength of the material is improved
in the unoriented zone6 which at the same time become
opaque. Furthermore, a combinatlon of the methods
indicated above results in an undesired oversizing of the
neck sections of the containers, whilst the latter at the
same time have poorer properties tnan the material in the
actual container body.
- The invention provides a blank which makes it
possible that, in a container formed from the blank, bot~
the mouth part and the neck sections and also the container
body consist of a material which is adapted to the
occurring stresses and in which the material in the said
parts is oriented to a satisfactory ~xtent in such a way
that the material is stretched, at least in the axial
direction, by a factor ol more than 3.
This results in the advantage o~ a raised glass .
transition temperature Tg in all the said parts of the
container. This means that all thesa~ parts will have
the same heat resistance, and this is a great advantage
compared with containers which are ~ormed according to
the known technology and which, at least as far as con-
tainers with mainly clear and transparent materials are
concerned, have neck sectlons and mouth parts which are
more sensitive to heat stresses than the actual container
body.
Moreover, the invention enables a.container o~
sm~L~rmouth diameter to be manu~actured, the length and
diameter of the container body being matched to the
storage capacity of the con-tainer in such a way that the
.
~2~
smallest possible ~lantity of material per unit volume of
storage space results.
In a~dition, the invention enables a container of
any desired shape of the neck part to be formed from the
blank, the container material in the mouth part and in the
neck part also being orientPd and having a crystallinity of
more than l~/o~ this was achieved by stretching the material
to the requisite extent, ~or example in the case of con-
tainers of PET by stretching in the axial direction by a
factor of more than 3. According to known technology it was
hitherto not possible to obtain such a degree of orienting,
unless the mouth part and neck sections of the containers
were to consist of mainly unoriented material, in which case
the neck sections merge in the shortest possible distance
with oriented sections of the container body, where the wall
thickness has been reduced by a factor of at least 3. This
shaping represented an attempt to reduce the size of that
zone in the neck part, which has mainly amorphous material
and low ori.entation and hence a low glass transition
temperature Tg~
In accordance with one aspect of the invention,
there is provided a tubular pre-moulding of a thermoplastic
material, the pre-moulding having a mouth part with adjacent
neck sections at one end, a closure at the other end and a
tubular section between the two ends, and the closed end
and the tubular section of the pre-moulding consisting
mainly of amorphous unoriented material having a
~Z~15
crystallinity of less than 5~0 The tubular pre-moulding of
the invention is characterized :in that the mouth part w.ith
adjacent neck sections of the p:re-moulding are orient~d
mainly in the axial direction o:E th~ pre-moulding by
reducing the wall thickness by a factor corresponding to
the reduction of thickness obtained in a sheet of the
material monoaxially stretched into yielding, the crystal-
.linity of the material in the mouth part and in the
adjacent neck sections being at most 50~0.
According to a further aspect of-the invention,
there is provided in a tubular pre moulding of a thermo-
plastic of polyester or polyamide type, the pre-moulding
having substantially uniform initial thickness and
comprising a mouth part with adjacent neck sections at
one end, a closure at the other end and a tubular section
between the two end~, the closed end and the tubular section
of the pre-moulding consisting mainly of amorphous unoriented
material having a crystallinity of less than 5%, the improve-
ment wherein the mouth part of the pre-moulding, with
adjacent neck sections, consists of material which is
oriented substantially by a reduction in the thickness of
the material while the remainder of the pre-moulding retains
its original thickness and, at least in the mouth part, the
material has a lower degree of orientation in the circum-
ferential direction of the pre-moulding as compared to the
axial direction. The crystallinity of the material in the
mouth part is at most 5~/0, the orientation of the mouth
- 12 -
-part and adjacent neck section~ of the pre-moulding by the
thickne~ reduction providing an increased glass transition
temperature Tg in the mouth part and neck sections which is
substantially equal to the glass transition temperature of
the tubular section when the amorphous material of the
tubular section is oriented by a subsequent blowing of the
pre-moulding to a container.
Accordiny to the invention! the tube of thermo-
plastic material is clamped in between two mutually separate
clamping devices. The material in the zone between the
two cla~ping devices is stretched in the axial direction
of the tube by shifting the clamping devices in the
direction away from one another. When PET is used,
stretching by a factor of at least 3 takes placeO
According to one embodiment of the invention, the
3~
~ 13
material in the tube is stretched, while the material is
at a temperature aboYe the glass transition temperature
Tg~ whereas in another embodiment the'material is stretched
in the cold state~ which means that the material is at a
temperature below the glass transition temperature Tg at
the beginning of the stretching step. On stretching
"in the cold state", the materia'l is drawn until flow sets
i~l .
After stretching, at least the central sections
of the drawn material are blow-moulded at a temperature
above the glass transition temperature Tg against a mould,
in order to form, for example, threads and9 in some cases
which may occur, parts of'the adjacent neck sections,
while two future mouth parts are in adjacent posiiions.
Subsequently, the tube is severed at the transition
between the two future mouth parts. Each of the two
severed blank parts thus produced form a tubular pre-
moulding, after closing at one end and 9 if appropriate,
reworking at the other end in order to obtain the requi'red
closure surfaces.
In optional embodiments of the invention, the
material is heated before the axi~l stretching to a tem-
perature above the glass transition temperature Tg, or
the stretching step is preceded by a blow-moulding step
in which the heated material is subjected to a certain
expansion in order to increase the diameter of the zone.
In another embodiment of the invention7 the mouth
parts of the pre-mouldings are shaped'by simultaneous
axial stretching, and blow-moulding for the purpose of a
- 14 -
radial expansion of the heated material-
In certain application examples, the heatedmaterial zone has a temperature profile such that one or
several annular zones are at a temperature which exceeds
the temperature of the adjacent material by ~-20C 9 pre-
ferably 10-15C. l~le actual drawing or stretching
step starts in the material ~ones of higher tempera~ure.
In an application of the invention, wherein the
material in the tube is,a* the start of axial stretching
of the maleria~ at a temperature which is less than the
glass transition temperature Tg, the drawing or stretching
step is initiated, according to an optional embodiment of
the invention, with the aid of pressure forces. This
is achieved, for example, by means of a ring which sur-
rounds the tube, the inner surface of thering being brough~
into contact with the outer surface of the tube by reducing
the internal diameter of the ring.
On axial stretching of the material, the external
diameter of the tube is reduced. As a result of the
invention, it is thus possible to produce a pre-moulding,
the mouth part of which has an external diameter which is
less than the çxternal diameter of the tu~e.
Equipment ~or carrying out the process comprises
a number of stretching and blow-moulding devices, which
are each provided with two clamping devices which are
located at a certain spacing from one another. The
clamping devices are provided for clamping a tube in, and
the two sets of clamping devices are arranged in such a
way that they can be shifted towards one another or away
~63
~5
from one another. The contact surfaces ~f the
cla~ping devices with the tube are oooled. Appro~
priate devices are provided fs~r heating the material in
the tube be~ween the said sets ofclamping devices, and
also the blow-moulds against which the heated material is
blown. Moreover, the equipment comprises elements
for closin~ the tro ends of the tube before blow-moulding
and also elements fsr applying an elevated pressure to
the slosed cavlty formed in this way. In certain
illustrative embodiments, a cylindrical rod is also
fitted axially in the tube. Finally, an element for
severing the tube into two pre~erably equal parts is
present.
In an embodiment of the invention, the clamping
devices are arranged in such a way that ~he tube can
rotate about its own axis. In this way 9 heating of
the material in the zone between the two sets of olamping
devices and also the severing of the tube into ~wo eq~al --
parts are facilitated.
In ~orming a blank, the tube is f ixed between the
two clamping devices, after which the latter are shifted
in the direction ~way from one another, in oertain illus-
trative embodiments after the material between the two
sets of clampin~ devices has first been heated to the
desired temperature profile and, in cer-tain application
cases, with simultaneous radial expansion of the material
in the tube or after a first radial expansion of the
material in the tube has taken place. The length of
displacement relative to the length of the part of the
tj
-- 16 --
tube, -~he material of which is stretched3 is selected in
the case of PET in such a way that the material reaches
a crystallinity of at least 10% on axial orientation.
In some cases w~ich may occur, the cylindrical rod is
introduced intc the tu~e before'the material is stretched.
In certain application examples, the rod is heated. To
effect radial expansion, the two ends of the tube are
closed, the material between the two sets of clamping
devices is'heated'in some cases which may occur, and the
closed space in the tube is subjected to pressure, the
heated material expanding in such a way that it makes
contact with the mould surfaces, for example for the pur-
pose of moulding the mouth thread and adjacent neck
sections. When the material has cooled to a sufficient
extent to reach dimensional stability, the tube is severed
into two parts in the severing element. - Each of the
two parts is closed at one end by reshaping and, if appro-
priate, reworked at the other end, that is to say the
mouth end, in order to produce th~ requisite closing sur-
faces~ Thus, the pre-moulding is completed.
According to the process described above, ea~h
drawing step with subsequent severing results in ~ro blan~
parts which~ after a certain rewor,king and reshaping 9 each
form a blank. In this manner, no losses of material
arise in the production of pre-mouldings. Of course,
the stretched material formed during the drawirg step can
be adapted in such a way that it is used for forming
exclusively one single future mouth part with adjacent
future neck sections. Due ~o ~he severing of parts of
~ 17 -
the piece of tube, which can :not be used for further
production of the pre-moulding, however, this leads to
undesired losses of material, so ~hat this embodiment of
the invention is only used in special cases~ for example
in the production of pre-mouldings which are.intended ~or
contalners having long mouth sections and neck sections.
Figure 1 shows, in perspective view, a stretching and
- blov-moulding device having ~wo sets of clamping
devices, and with the two sets o~ clamping
devices o~ the stretching device bei.ng in the
position ior receiving a piece of tube,
Figure 2 shows, in perspective view, a stretching and
blow-moulding device, with the clamping devices
in the position ~or fixing a piece of tube,
.Figure 3 shows a sectional view of the stretching and
. blow-moulding device during the heating o~ a
central part of a piece of tube,
Figure 4 shows a sectional view of a stretching and
blow-moulding device with the piece o~ tube
fixed and drawn,
Figure 5-shows a sectional view of a stretching and
blow-moulding device with the internal volume
of the piece of tube subjected to pressure in
order ~o form the mouth sections and adjacent
neck sections,
~igure 6 shows a device for severing ~he piece o~ tube
- - into two separate blank parts,
~igure 7 shGws, in diagrammatic view~ a device for the
stepwise produ~tion of blank parts for pre-
18 _
mouldingsO
Figure 8 shows a sectional view of a stretching and
- blaw-moulding device having a device for heating
an annular sestion in the piece of tube,
Figure 9 shows a secti~nal view of a stretching and .
blow-~oulding device during the cold-~rawing .
step of the piece of tube,
Figure 10 shows a sectional view of a stretching and
- blow-moulding device a~ter the cold-drawing
step of the piece of tube has been carried out,
Figure 11 shows a sectional view of a stretching and
blow-moulding device with the length of the
axially drawn zone increased,
Figure 12 shows a partial section through a stretching
and blow-moulding device according to Figure 11,
in which the internal volume c~ the piece-of
tube has been subjected to pressure, and in
particular the forming of the neck sections
- adjacent to the mouth part,
Figure 13 shows a completed tubular pre-moulding which
has been shaped from a blank part according to
Figure ~, and
- Figure 14 shows a completed tubular pre-moulding which
has been shaped from a blank part according to
Figure 12.
Figures 1 and 2 show a frame on which two separate
sets of clamping devices 20 a-b and 21 a-b are located.
I~ principle, the two sets of clamping devices consist of
an upper clamping part 20a, 21a and a lower clamping part
~lq3~ ~5
- 19 -
20b, 21b. In both sets of cl~mping devices~ the upper
part can be shifted between an open positlon and a closed
position. In ~e closed position, the particular set
o~ clamping devices fixes one end of a tube 50 in each
case~ The two sets o~ clamping devices can be shifted
from their starting positions (Figure 1) towards one
another up to a smallest distance ~Figure 2) which matches
the length of the tube 50, and from there they can be
shifted back again into the particular starting position.
-In the starting position, the particular upper part assumes
the open posi~ion and remains in the latter until the two
sets of clamping devices have been shifted towards one
another up to the said smallest distance. In this
position, the particular upper parts assume the closed
position and thus cover a relatively large part o~ ~he
tube 50, the latter being surrounded at the same time and
being fIxed by the particular set of clamplng devices.
While the upper parts are still in the closed position,
the two sets o~ clamping devices are subsequently shifted
back to the starting position. The shift of the upper
parts 20a, 21a of the-~wo sets of clamping devices is
effect~d by means of drive mechanisms 25, 26, and a drive
mechanism 24 is provided for shifting the two sets of
clamping devices towards one another. The two upper
parts slide in the grooves 22, 23 provided in the lower
parts; whilst the lower parts slide in grooves 13 a-b
provided in the frame llo . ~.
A gripper 28 is provided ~or inserting the tube
50 into the clamping devices or removing it from the
~2~
clamping devices. When the tWG sets-of clamping
devices are at their smallest distance from one anothrr,
a heating element consisting ~f the two heating jaws
29 a-b is brought int~ a position in which it can heat
the cen-tral sections o~ the tube 50. The motion of the
heating ja~s is effected by means of a drive mechanism 33
with a push-and-pull bar. A lead 31 for heating the,
heating jaws, ~or example by means of electric power, is
shown in the figures.
Adjoining one o~ the two sets of clamping devices,
a cylindrical forming and blowing mandrel 27 is provided.
This mandrel is moved by means of a drive mechanism 39
from and to a position in which the cylindrical part of
the mandrel protrudes a little into the opening of the
other set of clamping devices. The mandrel protrudes
into the said opening even when the two sets of clamping
devices are in their starting positions.
The external di~meter of the mandrel and the -
internal diameter of the tube 50 are matched in such a
way that the mandrel can be introduced into the tubeO
Moreover, the mandrel is provided with a row of orifices
40 which lead to a cavity in the interior of the mandrel~
which cavity is connected to a line 32 for a pressure
medium.
A pressure medium is fed via the lines 30a, b,
c, e (the pressure line 30d is not shown in the figure)
to the indivldual drive mechanisms 24, 25, 26, 33 and ~9.
In Figure 3, the two sets of clamping devices
20 a-b, ~1 a-b are shown in the position for the smallest
_ 21 -
distance between the sets. In addition, the figure
shows the said cavity 42 in the mandrel 27, a gasket 41
between one end o~ the tube 50 and t,he set of clamping
devices 21 a-~ a~d a gasket 34 ~e~ween the other end of
the tube 5G and the set of clamping devices 20 a-b.
A gasket 35 between the mandrel 27 and the set of clamping
devices 20 a-b can also be seen. An outle-t valve 36
is located in thP lower clamping device 21b. - In this
way, the closed space which can be subjected to pressure
through the orifices 40 is formed in the mandrel 27.
Figure 4 shows the two sets of clamping devices
shifted back into their starting positions, while the
surrounded parts o~ the tube 50 are still held firmly as
before. The Figure shows that the mandrel 27 continues to
projectinto the set ofclamping devices 21a-~ A central zon~
510fthe tube 50has been stretched inthe axial directionand
hasasmaller wall thicknessthan theremainderof the tube.
In Figure 5 7 the central zone 51 has been blow-
moulded against the mould 57 a-~. The shaping surface
o~ the mould corresponds to the form of two mouth parts
52 a-b, facing one another, for containers which are tobe
formed fromthe blanksand arein the process ofmanufact-~re.
Figure 6 shows the mandrel 27 in its siarting
position. A severing disc 58 is located in the position
for severing the tube 50, that is to say at the transition
between the two moulded mouth parts 52 a-b.
Figure 7 shows a turntable 7 which rotates about
a bearing 12~ Next to the turntable, a number o~
positions A-U is indicated. One frame 11 with the
associated set of c~amping devioes, drive mechanisms,
tubu~ar mandrel, heating device and the like according to
Figures 1-2 is located on the turntable for each position.
In the positions, the particular working step is indicated
diagrammatically by the posi'tion of mandrel, heating jaws,
sets of clamping devices and the like.
~ igure 8 shows an embodiment of the invention,
which is adapted preferably for so-calle~ cold-drawing of
the tube. An annular heating element 38 lS locatea
be~ween the two sets of clamping devices. By means o~
this heating element, the central sections of the tube 50
are heated to an elevated temperature over an annular
zone.
Fig~res9-lQ relate to the cold-drawing of the
tube 50. In Figure 9, the formation of a centrally
located drawn zone 53 has started, whilst in Figure 10
the entire centrally located dra~m zone 54 has been
formed.
`Figures 11 and 12 relate to a variant of ~he
invention wherein the centrally located zone 51a of the
tube 50 is longer than in the previously described
embodiments of the invention. The figures show only
one of the ~wo sets of clamping devices. Figure 11
sh~ws the position after drawing of the tube has been
completed, whilst Figure 12 shows the central zone-
51a (Figure 11) after it has been blow-moulded against
an outer mould 59. The moulding surface of the outer
mould corresponds tothe shape of t~ro mutually facing
mouth parts (only one, 52a, is shown in the figure) and
- 23 -
parts of the adjacent future neck section 60a of the
containers which are to be formed from the blanks and
are i~ the ~rocess of product;ion~ A zone 567 having
the~largest diameter in the moulded future neok sections,
pre~erably has a diameter which is at least three times
the original diameter of the tub~.
Figures 1~ and 14 show comp~et~rl tubular pre
mouldings, the pre-moulding according to Fi~lre 13 haying
been-formed from~a blank part shown in Figure 5 and a pre-
moulding according to Figure 14:having been formed from a.
blank part shown in Figure 12. At one end, the pre-
mouldings have a mouth part 62a, b with adaacent neck
sections 63a, b. At the other end the pre-mouldings
have a closure 61a, b. A tubular section 64a, b can
be seen between the closure 61a, b and the neck sections
63a1 b r
In the production ol a pre-moulding according to
the invention$ a tube 50 is brought into the position
sho~m in Figure 1 with the aid of the gripper 28. The -
two sets of clamping devices 20 and 21 are shifted
towards one another with the aid of the drive meohanism
24 until the ~wo ends of the tube are in contac~ with
the gaskets 34 and 41. The upper clamping devices
are brought into their closed position with the aid of
the drive mechanisms 25, 26, the tube 50 being firmly held
at both its ends and at the same time being enclosed over
a relatively large part. This situation is ~hown in
Figure 2. As an alternative, the mandrel 27 was
already in this phase brought beforehand into the position
6~s~ a ~
- ~4 -
which is shown in Figure 3~ The heati~g jaws 29 are -
brought into the heating position and remain in this
position for such a perio~ as-is necessary for heating
the material in the c`en~ral-sections o~ the tube to a
temperature below the glass transition temperature Tg~
The drive element 24 now shifts the ~wo sets of clamping
devices in the direction away from one another~ the
central sections of the tube being stretched; with
~simultaneous thinning of the tube wall, in such a way
that the tube is given the appearance shown in Figure 4.
Preferably, stretching amounts to at least a factor of 3,
and the reduction in thickness thus also amounts to a
factor of 3. During the entire drawing step; the
mandrel 27 is located in the interior of the tube, within
the stretched zone9 and thls prevents the stretched zone
from assuming an undesirably small diameter.
The closed space in the interior of the tube is
subjected to pressure, the material being expanded into
the zone concerned until it makes contact with t~e outer
mould 57. In~this step9 the future mouth parts and
parts of the adjacent neck sections in two blank parts
connected to ~ne another are shaped to give pre-mouldings.
On contact with the-surfaces of the outer mould, the
material in the tube is cooled so that it becomes dimen-
sionally stable. With simultaneous retraction of the
mandrel 27 into its starting position, the outer mould is
opened and a severing disc 28 divides the tube at the
transition be~een the two future mouth parts. This
produces two separate blank parts ~Jhich are closed at one
91.S
- 25 -
end by reshaping and are provided with the requisite
closing sur~aces a~ the other end by reworking. In
this way, a tubular-pre~moulding as shown in Figure 13
is obtained.
The design of the equipment for closing one end~
and likewise for the reworking, which may be necessar~,
of the mouth part7 is not shown in the figures~ but this
can be in accordance with any technology already known
and used. Normally~ closing is effected by ~eating
the material at one end of the tube u~ to a temperature
above the glass transition temperature Tg. after which the
end is forced in the axial direction against a substan-
tially spherical shell which compresses the soft material
and closes the end~ Subsequently, the gripper 28 takes
the two blank parts ~ormed out of the production equipment
after the two sets of clamping devices have released the
pre-mouldings. Subsequen~ly, the course of the pro-
cess described above is repeatea.
According to a pre~erred embodiment of the inven-
tion, the production step described above is carried out
with the aid of the equipment shown in ~igure 70 In
position A, th~ tube is fed to the t~Jo sets of clamping
devices, in position B the two sets of clamping devices
are shifted in the direction towards one another, whilst
simultaneously the mandrPl is introduced into the tube,
and in position C-E the central zone of the tube is heated,
whilst in positio~ ~ the heating process is interrupted.
In p~sitions G-H, the central sections of the tube are
stretched, irl position I the outer moulds move into the
~2~ iS
- 26 -
moulding position 7 in position J the interior o~ the
tube is subjected to pressure and is formed to give the
future mouth parts with the acljacent nec~ sections.
In position ~, the oute.r moulds open, whilst in position
L the mandrel is retracted into its starting position.
Position M is a cooling position for stabilising the
form o~ the tube or, alternatively, is a reserve
position, whils~ i~ position N the tube is severed into
~wo blank parts. In position 0, the -~wo future mouth
parts are heated for.reworking, i~ appropriate, and they
obtain their final form in position P. In position R,
the devices for reworking the mouth parts have assumed . -
again their starting position, and subsequently, in
position S~ the blank parts have been shifted in the
direction towards one another in order~to enable the
gripper to engage in position T and to enable ihe clamping
devices to open in position U, so tha~ the mouldings
formed can be removed ~r~m the production equipment
according to ~igure 7. Advanta~eously, the gri~per
device here transfers the blanks ~o devices for closing
one of their ends. Such devices can either be pro-
vided independently of the equipment described in this
paragraph, or they can form part of this equipment.
In the latter case, this equipment must be pro-
vided with a further number of positions.
During cold-drawing of the oentral zone of the
tube, the material is heated before the drawing step with
the aid of an annular heating element 38 (~igure 8~ over
an annular ~one within the central zone.. This heating
- 27 -
element is preferably designed to heat the central zone
as ~ar as one of the sets v~ clamping devices. To
con~rol the direction of displacement during the flow
which sets in on drawing 9 the material is normally cooled
immediately next to the heated annulus-in that dIrection
in which it is intended that the flow step should not
propagate. In the embodiments in which t,he entire
material of the tube is to be drawn between the two sets
of jaws, the required cooling is obtained by the cooled
jaws. In other embodiments, annular cooling devices
are used which, in princlple, are arranged in a manner
corresponding to the arrangement of the heaiing device 38.
On warm-drawing of the central zone o~ the tube,
one or several annular heating elements are used in cer-
tain application examples in order to produce the desired
temperature profile in the central zone of the tube before
the latter is drawn. The annular heating elements here
~requently consist o~ zones of elevated temperature in the
heating jaws 29.
On cold-drawing of the material in the central
zone o~ the tube, flow of the material sets in first in
the annular zone which has been heated by the annular
heating element ~8. On further stretching o~ the cen-
tral zone o~ the tube, the flow zone of-the material is
displaced in the direction of the other set of clamping
devices, comPare Figure 9 9 SO that, after completion of
the stretching step, a central drawn zone has formed, the
appearance of which is shown in Figure 10. On cold-
drawing, the central zone has no tendency towards a
.
- 28 -
reduction of the internal diiameter of the tube, as long
as stretching is~limited to ~bout a ~actor of 3. In
. this embodiment of the lnven-tion,-lt is ~hus not-necessary
to cause the mandrel 27 to assume its positivn in the tube
.
- before the actua7 stretching step~ Figures 11-12 show
an embodiment of the invention in which the stretched
central zone 51a has a greater leng-th than in the embodi-
men*s of the invention so far described. ~en the
interlor of the tu~e is subjected to pressure, parts of
. .... ~ .. .
adjacent neck sections are:also formed, in addition *o the
two future mouth parts, these neck sections being given a
greater diameter than that of the actual mouth part.
At this stage, it is pre~erable to allow the future neck
section to be shaped to such an extent that the greatest
rise in diameter is at ieast 3-fold. This-ha-s *he
advantage *hat a relatively dimensionally stable neck
section is formed which, during the subsequent heating in
conjunction with the shaping o~ the remaining part o~-the
container~ is affected only to a small ex~enc. ~he
appearance of a pre-moulding, which was formed from a
blank part partially shown in Figure 12, can be seen in
Figure 14.
In the above description9 it was explained how
the blank parts are formed by severing the drawn and
shaped tube. In a preferred embodiment of the invention,
severing of the blank parts from one another is effected
with the aid of one or several severing discs which
revolve under pressure about the circumferential surface
of the tube formed at the.transition between the ~wo
s
-- 2 9
future mouth parts.
It was ass~ed in the above description that
heating of the centra~ material sections of the tube is
ef~ected-by heating jaws. To obtain the most uniform
heating of the material possible, the tube should pre-
ferably rotate relative to the heating element. To
make this possible, the clamping devices are moAi~ied 7
if appropriate having cone type bearings or having heating
jaws which revolve about the tubeO
In the case where the central sections of the
tube are drawn at an initial temperature which is below
the glass transition temperature Tg, the material is
heated after the drawing step to a temperature above ~he
glass transition temperature Tg, after which the ~uture
mouth part and parts of the adjacent neck sections are
shaped.
- I~ addition to the above description, the inven-
tion is also comprised by the attached patent claims.
