Process and apparatus for temperature conditioning a thermoplastic blank

A method for temperature conditioning a blank of plastic material in which a conditioning mandrel is placed within the blank and thereafter expanded into reliable abutment against the inner surface of the blank. The mandrel is thereafter returned to its initial position. The outer surface of the mandrel is adjusted to and maintained at a certain temperature, whereby, during the abutment, an energy exchange takes place between the blank and the mandrel for adjusting the temperature of the blank. At high temperatures of the mandrel, the mandrel is displaced out of the blank after such short time that the plastic material in the region of the abutment surface never passes the critical temperature of tackiness of the plastic material and/or thermal crystallization of the plastic material. As a rule, the expansion and contraction of the mandrel is repeated one or more times.

FIELD OF THE INVENTION 
The present invention relates to a method and an apparatus for controlling 
heat treatment of a tubular plastic article by a mandrel inserted into the 
article. 
BACKGROUND AND PRIOR ART 
It is previously known to reform, using a mechanical tool, a blank of 
plastic material into an intermediate preform or into a container. 
Thus, it is known to reform a tubular blank into an intermediate preform by 
extending the blank in its axial direction which simultaneous orientation 
of its material. This takes place once the material in the blank has been 
set at an elevated temperature, whereafter, for example, a rod displaces 
the bottom of the blank relative to the mouth portion of the blank. 
U.S. Pat. No. 4,580,968 describes an alternative technique in which a 
tubular blank is reformed into an intermediate preform in which the 
material of the blank passes through a gap in a mechanical forming tool, 
the gap width being less than the material thickness of the blank. In such 
instance, a transition zone is moved in the axial direction of the blank 
between substantially amorphous plastic material (thick material) and 
oriented material (thin material) under the reduction of the amount of 
amorphous (thick) material and increase of the amount of oriented (thin) 
material. 
On displacement of the transition zone, the plastic material is oriented. 
This patent describes an embodiment in which the gap is formed between a 
draw ring and a mandrel located within the blank. Displacement of the 
transition zone is realized in that the mandrel displaces a blank placed 
on the mandrel in relation to the draw ring, amorphous material in the 
blank passing through the gap and being oriented in the direction of 
displacement of the transition zone. 
The above-described orientation of the plastic material in a blank by means 
of a mandrel and a draw ring is generally preceded by a setting of the 
temperature of the material at an elevated level. For example, for 
polyethylene terephthalate, hereinafter generally abbreviated to PET, a 
temperature is normally selected which slightly exceeds the glass 
transition temperature of the material, however, the temperature may also 
be in the region of or slightly less than the glass transition temperature 
of the material. Hereinafter, the designation TG will generally be 
employed to indicate the glass transition temperature of the plastic 
material. On entry into the above- mentioned gap, the material is 
generally at the elevated temperature. 
The material then passes through the gap, it being required that the 
contact surface of the material against the draw ring is at a temperature 
less than a certain maximum temperature. This permitted maximum 
temperature is determined by the material in the draw ring which forms an 
abutment surface against the plastic material in its transition zone and 
by the relevant plastic material. The above condition regarding maximum 
temperature of the plastic material also applies to the contact region 
between the plastic material and the mandrel disposed within the blank. A 
further requirement related to adjustment of the temperature of the 
plastic material is that such temperature adjustment must, for reasons of 
process engineering and also for reasons of production capacity, if 
possible be effected with as slight an influence as possible on the cycle 
time of the equipment and preferably without affecting this cycle time 
whatsoever. Naturally, this requirement is conditioned by the desire of 
maintaining the capital cost per produced unit as low as possible. 
Moreover, in certain physical applications there are requirements that the 
temperature of the plastic material display minimal variation from one 
blank to another. In the above-described orientation of plastic material 
by means of a gap, it is desirable for certain plastic materials that the 
material temperature vary by at most approx. 2.degree. C. 
EP 204 810 describes a technique in which a hot mandrel is inserted in a 
preform of thin plastic material and progressively heats the material 
during simultaneous expansion of the preform as the material of the 
preform is brought into abutment against and displaced over the outer 
defining surface of the mandrel. A drawback inherent in this technique is 
that the temperature of the mandrel must be kept relatively high, which, 
for certain plastic materials such as PET, leads to undesirably high 
friction. 
In all of the above-described physical applications, the plastic material 
is, as a rule, given an elevated temperature before the reforming 
operation, since the elevated temperature is normally a prerequisite to 
enable application of the technique involved and in order that the product 
obtain the contemplated properties. The heating is effected in accordance 
with prior art using radiation energy. Because of the characteristics of 
the plastic material, such heating has a low level of efficiency. In order 
to reduce the heating time, use is made, therefore, of high temperatures 
at the radiation source, which, however, leads to problems if the blank 
remains in the heating position for too long. Such unintentional extended 
heating time often occurs in disruptions in the production process, for 
example an interruption in any of the processing stages which follow after 
heating of the blank. Such undesirable extension of the heating time in 
operational disruption will often result in sticking of the blank in the 
heating position or, at worst, in the blank catching fire unless special 
measures are implemented to screen off or remove the blank from the 
radiation source when the unintentional disruption occurs. It is obvious 
that if a blank sticks in the equipment, a relatively lengthy disruption 
in production will occur, in particular if the heating devices must be 
cooled in order to enable removal of the stuck blank. Both such 
disruptions and extra arrangements included in the equipment to screen off 
the blank from the radiation source in connection with production 
disruptions entail extra costs which render production and, thereby, the 
product itself more expensive. 
It will be obvious to one skilled in the art that there are, in many 
technical contexts, needs for a rapid temperature conditioning of plastic 
material, often in combination with desires for slight deviation in the 
temperature of the material for which the temperature conditioning has 
been carried out. In addition, there are often requirements that the 
temperature of the material in all parts of the blank be at the 
predetermined temperature. The term "temperature conditioning" is also 
here taken to mean cooling of the plastic material. 
SUMMARY OF THE INVENTION 
The present invention seeks a method and an apparatus in which the above 
drawbacks are obviated and in which the above requirements have been 
satisfied. This is attained by a method and an apparatus in which the 
mandrel is expanded within the plastic blank to abut against the inner 
surface of the blank and after a determined abutment period, the mandrel 
is contracted. 
At excessively high temperatures of plastic material, a considerable 
increase in friction will generally occur on contact with metal, and often 
also a tendency to tackiness between the plastic material and the metal. 
In the case of PET for example, an increase by a factor of 10 of the 
friction will occur if the material temperature in the region of TG 
increases by approx. 10.degree. C. This is one of the reasons why prior 
art technology generally avoids, on heating of the plastic material in a 
blank, direct contact between the plastic material and mechanical heating 
tools and instead calls for the employment of radiation energy for the 
heating operation. A temperature conditioning of the material in the blank 
takes place according to the present invention by means of a mechanical 
tool which is displaced to a position within the blank. The mechanical 
tool is hereinafter also referred to as temperature conditioning device or 
first mechanical device. The device consists, in the region where it abuts 
against the blank, of a material of superior thermal conductive capacity, 
normally of metal. Since the temperature conditioning device abuts against 
the plastic material of the blank for but a short time, the 
above-mentioned tendency to tackiness will be avoided even though the 
device, in certain embodiments, is at a relatively high temperature. The 
direction of displacement of the device in relation to the plastic 
material is selected such that friction problems are avoided. The selected 
direction of displacement also entails the advantage that, for all of the 
material portions which are temperature conditioned, temperature 
adjustment takes place during a substantially equal length of time. When 
the possibility of employing a large temperature difference between the 
temperature conditioning device (the temperature conditioning mandrel) and 
the plastic material is employed, an extremely rapid transfer of energy 
will be achieved between the conditioning device and the plastic material. 
At high temperatures of the conditioning device, the abutment is limited to 
such a short time that the plastic material in the region of the abutment 
surface never passes the critical temperature at which adherence takes 
place between the plastic material and the material of the heating mandrel 
and/or thermal crystallization of the plastic material begins to occur. 
The supply of energy during the brief contact between the heating device 
and the plastic material continues once contact has ceased, at the same 
time as the temperature of the plastic material in the region most 
proximal the abutment surface of the blank begins to fall. Under continued 
displacement of the thermal energy towards the opposing side of the blank, 
a reduction of the temperature of the plastic material continues adjacent 
to that surface with which the blank abutted against the heating device. 
When the temperature reduction has continued so far that the risk of 
tackiness and/or thermal crystallization is eliminated, the same 
conditioning device or another conditioning device is once again displaced 
into the blank, being moved into abutment against the inner surface of the 
blank. A thermal transfer during a limited period of time once again takes 
place to the plastic material, whereby a further thermal wave commences 
its displacement towards the opposing side of the blank. In one preferred 
embodiment, energy supply to the material of the blank takes place on at 
least two mutually subsequent occasions. Each time and after the first 
occasion when energy is supplied to the material of the blank, the thermal 
energy from the immediately preceding occasion has reached material in the 
blank located a distance from the abutment surface of the blank 
corresponding to at least approx. 1/6, as a rule at least approx. 1/5 and 
preferably at least approx. 1/4 of the wall thickness of the blank. 
However, it has surprisingly established that, in certain physical 
applications, only one heating period is required, in particular when the 
material is thin and is heated to relatively low temperatures. 
As a rule, an individual blank abuts only once against each conditioning 
device. However, the inventive concept as herein disclosed also 
encompasses embodiments in which one and the same conditioning device 
abuts against the individual blank more than once, and in certain 
applications on all occasions. 
In one preferred embodiment of the present invention, the blank is placed, 
prior to the displacement in relation to the conditioning mandrel, in a 
holder which is also at an elevated temperature. The holder is disposed to 
be rotated about a center axis located outside the holder and, thereat, to 
be displaced to mutually subsequently located positions. In at least one 
of these positions--as a rule the second--a displacement of a conditioning 
mandrel takes place to a position within the blank. After the 
predetermined abutment time against the inner surface of the blank, the 
conditioning mandrel is withdrawn from the blank, whereafter the holder is 
rotated about its center axis to its next position. During this 
displacement, the migration of the energy wave commences towards the outer 
surface of the blank. After a predetermined time, a conditioning mandrel 
is once again displaced into the blank, energy being once again supplied 
to the plastic material of the blank. The mandrel is thereafter moved from 
the position within the blank, whereby the blank is given the possibility 
of being moved to the next position by means of the holder. The number of 
positions, abutment times and/or displacement speeds of the container are 
determined int. al. by the thickness of the plastic material in the blank, 
by the thermal conductivity of the plastic material, by the temperatures 
of the abutment surfaces of the conditioning mandrels, and by the 
temperature to which the plastic material is to be heated. 
It should be observed that the described embodiment with the blank placed 
in a holder which is rotated about a center axis located outside the 
holder gives the possibility of providing, in each position, one 
conditioning mandrel specific to that position, the mandrel being, for 
instance, set at a predetermined and specific temperature for the 
position, having a design specific to the position, having a pattern of 
movement specific to that position, etc. Hence, in certain embodiments 
temperature and/or material in the abutment surface of the mandrel vary 
from position to position. Hereby, the possibility is created of 
controlling both the abutment time of the plastic material in each 
separate position and of minimizing the risk of undesirable friction 
and/or tacking tendencies in each respective position. 
In physical applications of the present invention in which the plastic 
material of the blank is temperature conditioned in order that the 
material be of a suitable temperature for attenuation, for example be 
oriented in that it passes through a gap (for instance employing a 
technique corresponding to that described by way of introduction), one 
preferred embodiment of the present invention calls for the selection of 
the speed of the draw ring in relation to the plastic material of the 
blank to be lower in the initial stage of the displacement of the drawing 
ring than during the remainder of the forming process. Hereby, an energy 
wave will be established in the transition region between thick material 
and attenuated material occasioned by the thermal energy which is released 
in connection with the reduction of the material thickness. As a result of 
the selected low speed of displacement of the draw ring, this energy wave 
will have time to move in the plastic material such that this attains a 
temperature suited for the subsequent processing (the attenuation). When 
this has taken place, it has surprisingly proved possible to achieve a 
drastic increase of the speed of displacement of the draw ring. Thus, an 
increase by a factor of up to approx. 5 will be tolerated by the material 
without any injurious effect on the quality of the attenuated material. 
If, conversely, the initial drawing speed is too high, the energy wave 
will not have sufficient time to exercise its full effect. (This is 
probably because the speed of displacement of the draw ring exceeds the 
speed of propagation of the energy in the plastic material). 
Further purposeful embodiments of the present invention are disclosed in 
the appended subclaims. 
The present invention and its aspects will be more readily understood from 
the following brief description of the accompanying Drawings, and 
discussion relating thereto.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
Referring to the Drawings, there is one embodiment of the present 
invention, adapted to act on a blank 10 having a sealed bottom portion 11 
and a mouth portion 12. The blank has an inwardly facing bottom surface 13 
and an inwardly facing, generally substantially cylindrical or slightly 
conical surface 14 which defines the wall 15 of the blank. If surface 14 
is conical, its largest circumference is in the mouth portion 12. The 
outer surface of the wall is designated by reference numeral 17. FIG. 5b 
shows how the blank has been partially subjected to a reforming, operation 
whereby there is formed a thinner wall portion 16a in the lower region of 
the blank, while the remaining wall portion 16b still retains its original 
form. A transition region 18 is to be found between the wall portion of 
original thickness and the wall portion of reduced thickness. 
A receiving device 30 (cf. FIGS. 1a and 1b), which also constitutes a 
holder for the blank, has a side wall 31 whose inner defining surface 32 
is of a size and configuration which substantially correspond to the outer 
configuration of the wall 15 of the blank. Channels 38 for a thermal 
medium (heat carrying medium) are disposed in the side wall. A substrate, 
for example a plate 33, is located beneath the side wall 31 of the holder 
for supporting the blank. 
A mechanical device which, in the Figures, is shown as a mandrel 20 (cf. 
FIG. 1b), hereinafter non-restrictively designated as a conditioning 
mandrel, 11 is connected through the intermediary of a drive shaft 21 to 
drive means (not shown). The drive means are disposed to displace the 
mandrel from the position illustrated in FIG. 1b, in which the mandrel is 
located above the blank, to the position illustrated in FIG. 2, in which 
the mandrel is inserted in the blank. The conditioning mandrel is disposed 
to be adjusted to a certain temperature which is adapted to that 
temperature at which the material of the blank is to be set. To this end, 
the conditioning mandrel is provided with ducts 28 for a heat carrying 
medium. In certain physical applications, the mandrel placed within the 
blank emits energy to the blank, while in other physical applications, the 
mandrel removes energy from the blank. The outer defining surface (side 
surface) 26 of the conditioning mandrel is dimensioned so as to have a 
configuration substantially corresponding to the configuration of the 
inwardly facing defining surface 14 of the blank. However, as a rule the 
dimensions of the blank vary from one blank to another, for which reason 
the conditioning mandrel is, in one preferred embodiment, provided with a 
first mandrel portion 22 and a second mandrel portion 23 which, by drive 
means (not shown), are displaceable from one another for increasing the 
circumference of the conditioning mandrel. The mandrel portions are, in 
this instance, separated from one another at the longitudinal section 24. 
It will be obvious to one skilled in the art that, in certain embodiments, 
use is made of more than two mandrel portions particularly in physical 
applications in which the variation of the circumference of the 
conditioning mandrel is great. The mandrel is defined by a bottom surface 
25. As is apparent from FIG. 3, at least one gap 27 is formed between the 
mandrel portions upon their displacement from one another. 
FIGS. 4, 4a, 5a and 5b show the receiving device, the holder 30, in 
cooperation with an orientation mandrel 60 which, via a drive shaft 61, is 
connected to drive means (not shown). The mandrel has outer dimensions 
corresponding to the inner dimensions of the blank 10, which entails that, 
with the mandrel placed in the position illustrated in FIG. 4, the side 
surface 66 of the mandrel abuts, at least with its lower portion, against 
the inner surface 14 of the blank. Channels 68 are provided in the 
orientation mandrel for adjusting the temperature of the side surface 66 
of the orientation mandrel. The bottom surface 65 of the mandrel is 
disposed to abut against the inwardly facing bottom surface 13 of the 
blank. 
FIGS. 4, 4a, 5a and 5b show how the substrate 33 is provided with an 
aperture 35 of a size allowing the blank to pass through the aperture. In 
association with the aperture, there is provided a draw ring 50 with a 
circumferential region 51 in which the inner circumference of the draw 
ring is reduced from a larger size most proximal the blank to a smaller 
size more distal from the blank (cf. FIG. 4a). This circumferential region 
is defined towards the center of the aperture by a working surface 52. 
Just as the side wall 31 of the holder is provided with one or more 
channels 38 for heat carrying medium, the drawing ring 50 is provided with 
one or more channels 58 for adjusting the temperature of the working 
surface 52 of the draw ring. With the draw ring inserted in the aperture 
(cf. FIG. 5a) a gap 54, hereinafter referred to as a draw ring gap, is 
formed between the draw ring and the orientation mandrel, the gap having a 
width which is less than the material thickness of the blank 10. 
FIG. 6 shows one preferred embodiment of the present invention in which the 
substrate plate 33 is disposed under a composite unit 37 formed by a 
number of reception cups (holders) 30a-30e, which are secured to one 
another connection devices 36. In such instance, the holders are generally 
designed as substantially cylindrical tubes 30a-30e open at both ends. The 
composite unit is connected, via the devices, connected to a center shaft 
34 about which drive means (not shown) rotate the unit to predetermined 
positions in which the combinations of devices described with reference to 
FIGS. 1-5 are formed. In certain physical applications, the center shaft 
is fixedly connected to the composite unit so as to rotate it. The 
movement of rotation about the center of the composite unit is, in this 
instance, indexed such that the holders are located, with preadjustable 
intervals, in one of the positions indicated by reference numerals 1-5. 
The displacement of the holders to positions 1-5 takes place by relative 
movement in relation to the substrate 33 which, as a rule, is in a fixed 
position. 
In position 1, which has its counterpart in FIG. 1a, the blank 10 is 
received by the receiving device (the holder) 30a which, in FIG. 6, is 
located in position 1. Positions 2, 3 and 4 each correspond to those 
combinations of devices as are illustrated in FIGS. 1b, 2 and 3; and 
position 5 has its counterpart in the combination of devices shown in 
FIGS. 4, 5a and 5b. In the region corresponding to position 5 for the 
holder 30, the plate 33 is provided with the aperture 35 and the draw ring 
50. In the illustrated embodiment, the apparatus allows for temperature 
conditioning of the blank at a maximum of 3 occasions as necessary. 
The apparatus includes control and regulation means (not shown) for 
controlling and regulating the movements and expansion of the conditioning 
mandrel and, in this instance, also the time interval during which the 
abutment of the mandrel proceeds. The control and regulation means (not 
shown) are also disposed for adjustments of the temperature of the medium 
supplied to the conditioning mandrel 20, the holder 30 and, where 
applicable, the draw ring 50. 
When the present invention is reduced into practice, the blank 10 is 
displaced into the receiving device (the holder 30a) to the position 
illustrated in FIG. 1a. Thereafter, the composite unit 37 is rotated 
through one position, whereby the holder 30a is moved to position 2. 
During this displacement, the holder slides on the upper defining surface 
of the plate 33. In position 2, the conditioning mandrel 20 is displaced 
from an upper position (cf. FIG. 1b) to a lower position (cf. FIG. 2). In 
the upper position, the conditioning mandrel is located above and outside 
the blank, and in the lower position within the blank. In one preferred 
embodiment, the conditioning mandrel is dimensioned so as, with its outer 
defining surface 26, to form a gap 41 with the inner defining surface 14 
of the blank. As a result, the inwardly facing surface 14 of the blank is 
prevented from coming into contact with the mandrel 20 during its movement 
into the blank and this, thereby, avoids the risk of, for instance, 
uncontrolled heating of the material of the blank and consequential risk 
of undesirable friction between the mandrel and the plastic material. 
In view of the varying sizes of the blanks, the holder is, in one preferred 
embodiment, also dimensioned to form a gap 40 between itself and the 
outwardly facing defining surface 17 of the blank. The conditioning 
mandrel is thereafter expanded into abutment against the inner defining 
surface of the blank and, as a rule, thereafter an additional distance to 
displace material of the blank outwardly into reliable abutment against 
the inwardly facing defining surface 32 of the holder. The expansion of 
the conditioning mandrel is controlled so as to continue until the blank 
abuts with its outer surface against the inner surface of the holder. By 
such means, there will be achieved reliable contact between the 
conditioning mandrel and the blank and between the holder and the blank, 
and efficient control of the energy transfer between the blank, the 
mandrel and the holder, respectively. In one preferred embodiment, use is 
made of a relatively slight degree of expansion, as a rule limited to at 
most approx. 20% and preferably to at most approx. 10%. In case of slight 
expansion, but a limited number of mandrel parts are required, while in 
case of a greater degree of expansion, the number of mandrel parts is 
increased so as to reduce the width of those gaps which are formed on 
expansion between the mandrel parts. As a result, there will be ensured a 
uniform heating of the plastic material. The temperature of the abutment 
surfaces of the mandrel against the blank are adjusted by means of heat 
carrying medium in the ducts 28 and channels 38 of the conditioning 
mandrel and holder, respectively. 
The following example of employed temperatures and times may be given for 
temperature conditioning of PET. The temperature of the outer surface 26 
of the conditioning mandrel 20 is, as a rule, in excess of the region of 
TG and in such instance, by at least 10.degree. C., as a rule by at least 
30.degree. C. and preferably by at least 50.degree. C. Control and 
regulation means are employed to adjust the time for the abutment of the 
conditioning mandrel against the inner surface of the blank, this being 
selected to be at most approx. 5 sec., normally at most approx. 3 sec. and 
preferably at most approx. 2 sec. Naturally, the abutment time employed is 
adapted to the temperature of the conditioning mandrel and the properties 
of the plastic material. The temperatures and times disclosed in this 
paragraph relate to temperature conditioning of a blank of PET whose wall 
thickness is of the order of magnitude of 2 mm. It will be obvious that, 
for other plastic materials and/or other dimensions of the blank, the 
conditioning time will be adapted to meet the relevant situation. 
Once the conditioning mandrel has abutted against the blank during the 
predetermined time, the mandrel is contracted and withdrawn from the 
blank. The blank is then displaced to the next position where, in 
applicable cases, a new abutment of the conditioning mandrel of this 
position takes place against the material of the blank for exchange of 
thermal energy between mandrel and blank. Also in this position, the 
abutment time is governed in analogy with that disclosed in the preceding 
paragraph. It will be obvious that the cycle for the temperature 
conditioning of the blank may be repeated in one individual station by 
allowing the mandrel to run through the above-disclosed schedule more than 
once with the holder remaining in the same position. 
Having passed the positions for temperature conditioning, the blank is 
moved to position 5. As a rule, the blank rests in this position on the 
working surface 52 of the draw ring 50 (cf. FIG. 4a). When the blank has 
assumed its location in position 5, the orientation mandrel 60 is 
displaced downwardly and through the aperture 35 in the base plate 33, 
whereupon the bottom surface 65 of the mandrel, on abutment against the 
inwardly facing bottom surface 13 of the blank, displaces this surface, 
and thereby also the blank 10, through the aperture. At this point, the 
gap 54 is formed between the orientation mandrel 60 and the draw ring 50, 
the size of this gap being less than the thickness of the wall 15 of the 
blank. On passing through the gap, the material in the wall abuts against 
the working surface 52 of the draw ring 50, whereby, in conjunction with 
the passage into the gap, the material thickness of the wall of the blank 
is reduced and tensile forces are applied to on the material in the blank 
in the axial direction of the blank. A transition zone is formed between 
thin (as a rule oriented) material which has passed through the gap, and 
thick (as a rule generally amorphous) material which has not yet passed 
through the gap. On displacement of the orientation mandrel, the 
transition zone is shifted into the amorphous material. Hereby, the 
material in the wall 15 is oriented in an axial direction when the 
material passes the working surface 52. Depending upon the desired 
application of the invention, all material in the blank is oriented or 
only a part thereof. In practical applications in which reduced material 
thickness is imparted to all of the material in the wall of the blank, the 
reformed blank is located beneath the draw ring once the movement of the 
orientation mandrel is completed. A channel 62 for pressure medium is 
provided for releasing the reformed blank from the orientation mandrel. 
Once the orientation mandrel has returned to its starting position, the 
holder 30 is displaced to position 1, whereafter the above cycle is 
repeated. 
The temperature of the holder 30 is generally adjusted to a level which at 
most amounts to a temperature at which the thermoplastic material begins 
to thermocrystallize. As a rule, adjustment is therefore effected at a 
temperature within the range of the TG of the thermoplastic material, but 
in certain embodiments at a temperature which is less than TG. For PET a 
temperature of at most approx. 85.degree. C., preferably at most approx. 
80.degree. C., has proved to entail good temperature distribution in the 
wall of the blank. 
Since all of the mechanical devices which are in contact with the plastic 
material consist of material with a good coefficient of thermal 
conductivity (as a rule metals) there will be achieved according to the 
invention an adjustment and control within narrow tolerance limits of the 
temperature of the thermoplastic material in all stages of the 
above-described cycle. This is particularly important in the transition 
region 18 of the wall of the blank where, in conjunction with the 
reduction of material and prevailing orientation, energy is released which 
needs to be removed. Since the plastic material abuts against the 
orientation mandrel 60, against the holder 30 and against the working 
surface 52, the material is, also in this critical region, wholly enclosed 
by material possessing good thermal conductivity properties, which makes 
for the requisite transfer of energy between the thermoplastic material 
and the mechanical devices. It will further be apparent from the above 
description that also before its passage through the draw ring, the 
thermoplastic material is, by means of the holder wall 31 of the 
mechanical devices, the conditioning mandrel 20 and the orientation 
mandrel 60, respectively, given a temperature adapted to those conditions 
which apply in order that the desired reduction of the thickness of the 
thermoplastic material and orientation (crystallization) through the 
material shall take place on passage by the blank of the draw ring. 
Both during passage through the gap 54 and thereafter--for example during 
the previously described temperature conditioning cycle--the side wall 31 
of the holder 30 has, via its defining surface 32 facing the blank, 
influenced the temperature distribution within the blank. In certain 
practical applications and/or positions, the defining surface 32 is at a 
lower temperature than the side surface 26 of the conditioning mandrel 20 
while in other practical applications and/or positions, the defining 
surface 32 is at a temperature which exceeds the surface temperature of 
the side surface 26 of the conditioning mandrel. In the normal case, the 
side surface 26 of the holder is at a temperature which is less than, or 
in the region of, TG. 
On displacement by the drive means of the orientation mandrel 60 through 
the aperture 35, the orientation mandrel displaces the closed bottom 
portion 11 of the blank ahead of it, at the same time as the orientation 
mandrel forms, between itself and the draw ring 50, the gap 54 whose size, 
in the case of PET, at most amounts to approx. half of the material 
thickness of the original blank, which consists substantially of amorphous 
material. This is taken to mean thermoplastic material of a crystallinity 
at most amounting to approx. 10%. As a result of the relative displacement 
of the orientation mandrel 60 in relation to the draw ring 50 and thereby 
the displacement of the bottom portion of the blank, the wall of the blank 
is forced to pass through the gap, 54 whereby the thickness of the wall of 
the blank is reduced along with the simultaneous monoaxial orientation of 
the material of the blank. Thus, during displacement of the orientation 
mandrel, the amount and length of the monoaxially oriented material are 
progressively increased while, at the same time the amount and length of 
the amorphous material are reduced. In practical applications in which all 
material in the wall of the blank passes through the gap, all material in 
the wall will, thus, be oriented. By means of the channels 38, 58 and 68 
in the wall 31 of the holder 30, in the draw ring 50 and in the 
orientation mandrel 60, respectively, the temperature of the material in 
the transition region 18 is controlled. Hence, it applies that for 
amorphous material, i.e. material which has not yet passed through the 
gap, a final adjustment of the temperature of the material of the blank is 
effected by means of the orientation mandrel 60 and the side wall 31 of 
the holder 30. During the orientation process proper, the draw ring 50 
plays an active role in drawing off that thermal energy which is developed 
in connection with orientation of the material, but also the orientation 
mandrel 60 itself assists in preventing the temperature from passing that 
temperature range within which the contemplated orientation is achieved. 
In the embodiment illustrated in FIG. 6, the system is stepwise rotated by 
the holder about the center shaft 34. Each time the system stops, one 
operation is executed. In position 1, the holder 30 is loaded with the 
blank consisting substantially of amorphous material. In the next step, 
the holder is moved to position 2 where the blank undergoes heating or 
cooling in accordance with that described above with reference to FIGS. 
1b-3. Thereafter, the blank is displaced to positions 3 and 4, 
respectively, where a corresponding treatment is repeated, in applicable 
cases. Finally, the blank is displaced to position 5 where the temperature 
conditioning and reforming of the blank described with reference to FIGS. 
4 and 5 take place. In order to enable this reforming, the substrate, i.e. 
the plate 33, is, in position 5, provided with an aperture corresponding 
to the aperture 35 in FIG. 4. When the orientation mandrel has been 
displaced to its lowermost position and all material in the blank has 
passed through the gap between the orientation mandrel and the draw ring, 
compressed air is generally employed to release the reformed blank from 
the orientation mandrel. This is achieved in that the orientation mandrel 
is provided with a channel 62 through which the compressed air passes and 
whereby the reformed blank is blown free of the orientation mandrel. 
Thereafter, the orientation mandrel returns to its starting position. 
In certain embodiments, the channels and ducts for heat carrying medium are 
replaced by electric resistor wires. The channels and ducts for said 
medium are generally employed only when the holder 30 or the orientation 
mandrel 60, respectively, is used for cooling material in the blank. 
In the foregoing, the invention has been described in connection with 
temperature conditioning of a blank whose material thickness is to be 
reduced in that the blank is to pass through gap 54. It will, however, be 
obvious to one skilled in the art that the technique described above is 
suited for application for temperature conditioning of plastic material as 
a preparatory measure for reforming a blank into a container irrespective 
of the prior art technique employed for such reforming. 
The above detailed description has referred to but a limited number of 
embodiments of the present invention, but it will be readily perceived by 
those skilled in the art that the inventive concept as herein disclosed 
encompasses a large number of embodiments without departing from the 
spirit and scope of the appended claims.